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Cloud computing security – Wikipedia

Cloud computing security or, more simply, cloud security is an evolving sub-domain of computer security, network security, and, more broadly, information security. It refers to a broad set of policies, technologies, and controls deployed to protect data, applications, and the associated infrastructure of cloud computing.

Cloud computing and storage solutions provide users and enterprises with various capabilities to store and process their data in third-party data centers.[1] Organizations use the Cloud in a variety of different service models (SaaS, PaaS, and IaaS) and deployment models (Private, Public, Hybrid, and Community).[2] There are a number of security concerns associated with cloud computing. These issues fall into two broad categories: security issues faced by cloud providers (organizations providing software-, platform-, or infrastructure-as-a-service via the cloud) and security issues faced by their customers (companies or organizations who host applications or store data on the cloud).[3] The responsibility is shared, however. The provider must ensure that their infrastructure is secure and that their clients data and applications are protected, while the user must take measures to fortify their application and use strong passwords and authentication measures.

When an organization elects to store data or host applications on the public cloud, it loses its ability to have physical access to the servers hosting its information. As a result, potentially sensitive data is at risk from insider attacks. According to a recent Cloud Security Alliance Report, insider attacks are the sixth biggest threat in cloud computing.[4] Therefore, Cloud Service providers must ensure that thorough background checks are conducted for employees who have physical access to the servers in the data center. Additionally, data centers must be frequently monitored for suspicious activity.

In order to conserve resources, cut costs, and maintain efficiency, Cloud Service Providers often store more than one customer’s data on the same server. As a result, there is a chance that one user’s private data can be viewed by other users (possibly even competitors). To handle such sensitive situations, cloud service providers should ensure proper data isolation and logical storage segregation.[2]

The extensive use of virtualization in implementing cloud infrastructure brings unique security concerns for customers or tenants of a public cloud service.[5] Virtualization alters the relationship between the OS and underlying hardware – be it computing, storage or even networking. This introduces an additional layer – virtualization – that itself must be properly configured, managed and secured.[6] Specific concerns include the potential to compromise the virtualization software, or “hypervisor”. While these concerns are largely theoretical, they do exist.[7] For example, a breach in the administrator workstation with the management software of the virtualization software can cause the whole datacenter to go down or be reconfigured to an attacker’s liking.

Cloud security architecture is effective only if the correct defensive implementations are in place. An efficient cloud security architecture should recognize the issues that will arise with security management.[8] The security management addresses these issues with security controls. These controls are put in place to safeguard any weaknesses in the system and reduce the effect of an attack. While there are many types of controls behind a cloud security architecture, they can usually be found in one of the following categories:[8]

It is generally recommended that information security controls be selected and implemented according and in proportion to the risks, typically by assessing the threats, vulnerabilities and impacts. Cloud security concerns can be grouped in various ways; Gartner named seven[9] while the Cloud Security Alliance identified fourteen areas of concern.[10][11] Cloud Application Security Brokers (CASB) are used to add additional security to cloud services.[12]

There are a number of security threats associated with cloud data services, not only covering traditional security threats, e.g., network eavesdropping, illegal invasion, and denial of service attacks, but also including specific cloud computing threats, e.g., side channel attacks, virtualization vulnerabilities, and abuse of cloud services. To throttle the threats the following security requirements are to be met in a cloud data service.[14]

Data confidentiality is the property that data contents are not made available or disclosed to illegal users. Outsourced data is stored in a cloud and out of the owners’ direct control. Only authorized users can access the sensitive data while others, including CSPs, should not gain any information of the data. Meanwhile, data owners expect to fully utilize cloud data services, e.g., data search, data computation, and data sharing, without the leakage of the data contents to CSPs or other adversaries.

Access controllability means that a data owner can perform the selective restriction of access to his data outsourced to cloud. Legal users can be authorized by the owner to access the data, while others can not access it without permissions. Further, it is desirable to enforce fine-grained access control to the outsourced data, i.e., different users should be granted different access privileges with regard to different data pieces. The access authorization must be controlled only by the owner in untrusted cloud environments.

Data integrity demands maintaining and assuring the accuracy and completeness of data. A data owner always expects that his data in a cloud can be stored correctly and trustworthily. It means that the data should not be illegally tampered, improperly modified, deliberately deleted, or maliciously fabricated. If any undesirable operations corrupt or delete the data, the owner should be able to detect the corruption or loss. Further, when a portion of the outsourced data is corrupted or lost, it can still be retrieved by the data users.

Some advanced encryption algorithms which have been applied into the cloud computing increase the protection of privacy.

In the CP-ABE, the encryptor controls access strategy, as the strategy gets more complex, the design of system public key becomes more complex, and the security of the system is proved to be more difficult. The main research work of CP-ABE is focused on the design of the access structure.[15]

In the KP-ABE, attribute sets are used to explain the encrypted texts and the private keys with the specified encrypted texts that users will have the left to decrypt.[16]

Fully Homomorphic encryption allows straightforward computations on encrypted information, and also allows computing sum and product for the encrypted data without decryption.[17]

Searchable Encryption is a cryptographic primitive which offers secure search functions over encrypted data. In order to improve search efficiency, an SE solution generally builds keyword indexes to securely perform user queries. Existing SE schemes can be classified into two categories: SE based on secret-key cryptography and SE based on public-key cryptography.

Numerous laws and regulations pertain to the storage and use of data. In the US these include privacy or data protection laws, Payment Card Industry Data Security Standard (PCI DSS), the Health Insurance Portability and Accountability Act (HIPAA), the Sarbanes-Oxley Act, the Federal Information Security Management Act of 2002 (FISMA), and Children’s Online Privacy Protection Act of 1998, among others.

Similar laws may apply in different legal jurisdictions and may differ quite markedly from those enforced in the US. Cloud service users may often need to be aware of the legal and regulatory differences between the jurisdictions. For example, data stored by a Cloud Service Provider may be located in, say, Singapore and mirrored in the US.[18]

Many of these regulations mandate particular controls (such as strong access controls and audit trails) and require regular reporting. Cloud customers must ensure that their cloud providers adequately fulfil such requirements as appropriate, enabling them to comply with their obligations since, to a large extent, they remain accountable.

Aside from the security and compliance issues enumerated above, cloud providers and their customers will negotiate terms around liability (stipulating how incidents involving data loss or compromise will be resolved, for example), intellectual property, and end-of-service (when data and applications are ultimately returned to the customer). In addition, there are considerations for acquiring data from the cloud that may be involved in litigation.[21] These issues are discussed in Service-Level Agreements (SLA).

Legal issues may also include records-keeping requirements in the public sector, where many agencies are required by law to retain and make available electronic records in a specific fashion. This may be determined by legislation, or law may require agencies to conform to the rules and practices set by a records-keeping agency. Public agencies using cloud computing and storage must take these concerns into account.

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Cloud storage – Wikipedia

This article is about enterprise-level cloud data storage. For consumer-level file hosting services, see file hosting service.

Cloud Storage is a model of data storage in which the digital data is stored in logical pools, the physical storage spans multiple servers (and often locations), and the physical environment is typically owned and managed by a hosting company. These cloud storage providers are responsible for keeping the data available and accessible, and the physical environment protected and running. People and organizations buy or lease storage capacity from the providers to store user, organization, or application data.

Cloud storage services may be accessed through a co-located cloud computer service, a web service application programming interface (API) or by applications that utilize the API, such as cloud desktop storage, a cloud storage gateway or Web-based content management systems.

Cloud computing is believed to have been invented by Joseph Carl Robnett Licklider in the 1960s with his work on ARPANET to connect people and data from anywhere at any time.[1]

In 1983, CompuServe offered its consumer users a small amount of disk space that could be used to store any files they chose to upload.[2]

In 1994, AT&T launched PersonaLink Services, an online platform for personal and business communication and entrepreneurship. The storage was one of the first to be all web-based, and referenced in their commercials as, “you can think of our electronic meeting place as the cloud.”[3]Amazon Web Services introduced their cloud storage service AWS S3 in 2006, and has gained widespread recognition and adoption as the storage supplier to popular services such as Smugmug, Dropbox, Synaptop and Pinterest. In 2005, Box announced an online file sharing and personal cloud content management service for businesses.[4]

Cloud storage is based on highly virtualized infrastructure and is like broader cloud computing in terms of accessible interfaces, near-instant elasticity and scalability, multi-tenancy, and metered resources. Cloud storage services can be utilized from an off-premises service (Amazon S3) or deployed on-premises (ViON Capacity Services).[5]

Cloud storage typically refers to a hosted object storage service, but the term has broadened to include other types of data storage that are now available as a service, like block storage.

Object storage services like Amazon S3 and Microsoft Azure Storage, object storage software like Openstack Swift, object storage systems like EMC Atmos, EMC ECS and Hitachi Content Platform, and distributed storage research projects like OceanStore[6] and VISION Cloud[7] are all examples of storage that can be hosted and deployed with cloud storage characteristics.

Cloud storage is:[6]

Outsourcing data storage increases the attack surface area.[17]

Companies are not permanent and the services and products they provide can change. Outsourcing data storage to another company needs careful investigation and nothing is ever certain. Contracts set in stone can be worthless when a company ceases to exist or its circumstances change. Companies can:[21][22][23]

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Bitcoin Wikipdia

A bitcoin egy nylt forrskd digitlis fizeteszkz, amelyet 2009. janur 3-n egy ismeretlen (frumos nevn Satoshi Nakamoto) bocstott ki, kzvetlenl a 2008-as amerikai bankvlsg kirobbansa utn. Az elnevezs vonatkozik tovbb a fizeteszkzt kezel nylt forrskd szoftverre, s az azzal ltrehozott elosztott hlzatra is.

A tbbi elektronikus fizeteszkztl eltren a bitcoin nem fgg kzponti kibocstktl s hatsgoktl. A bitcoin a peer-to-peer hlzat csompontjai ltal trolt elosztott adatbzisra tmaszkodik. Az adatbzis tartalmazza a fizetsek adatait, garantlva az elektronikus fizeteszkzkkel szembeni alapvet kvetelmnyeket. A biztonsgot digitlis alrsok s proof-of-work rendszer adja.[2]

A bitcoinok biztonsgosan trolhatk egy pnztrcafjlban, szemlyi szmtgpen, mobiltelefonon, kls adathordzkon, vagy felh alap szolgltatknl, kldskhz s fogadsukhoz pedig csak a kld illetve a fogad bitcoincme szksges. A peer-to-peer felpts s a kzponti irnyts hinya megakadlyozza brmilyen hatsg szmra, hogy a forgalomban lev pnzmennyisget s tranzakcikat kontrolllja vagy befolysolja, ami lehetetlenn teszi a manipulcit s inflci gerjesztst.

Nem hivatalos jellege miatt ISO kdja nincs, de ltalnosan hasznlt megjellse a BTC.

A bitcoint szmos erre specializldott devizatzsde weblapon lehet amerikai dollrra s nhny ms devizra tvltani, illetve vissza, fizetsnl online es “offline” kereskedk/szolgltatk egyarnt elfogadjk, szmuk jelentsen n. Egyes szolgltatk lehetv teszik kereskedk szmra bitcoin elfogadst olyan mdon, hogy a keresked azonnal dollrban vagy egyb szoksos devizban kapja meg a bevtelt. Ezen kvl hasznlhat kzrdek felajnlsokra egyes szervezeteknl.[3]

Mivel a fizets nem egy kzponton keresztl zajlik, a mr megtrtnt tranzakcik visszafordtsra nincs md, szemben a hagyomnyos banki rendszerekkel, ahol csals gyanja esetn, vagy egyb okokbl a bankok s ms pnzintzetek sztornzhatjk a korbban jvhagyott kifizetst.

Ellenttben az orszgok ltal kibocstott fizeteszkzkkel, a bitcoinnak nincs kzponti kibocstja, amely az rfolyam stabilits vagy egyb rdekek szerint intervencit, vagy egyb akcit hajtana vgre.[4] 2013 novemberig valamivel tbb mint 12 milli bitcoin jtt ltre, ezt a szmot a hlzat algoritmikusan hatrozza meg, ahogy azt Nakamoto cikkben lerta. A monetris bvls mrtke elre ismert s brki szmra kvethet, az sszes bitcoinok szma idvel 21 millihoz tart, 2013-ra a teljes mennyisg fele, 2017-re hromnegyede fog rendelkezsre llni. A hatr kzeledtvel a bitcoinok rtke nvekedni kezdhet, deflcihoz vezetve, amennyiben a pnzre a kereslet tovbb n. Ugyanakkor a bitcoinok 8 tizedesjegyig oszthatak, gy ez technikai akadlyt nem jelent, szemben a megszokott pnzeszkzkkel.

A bvls cskken teme sztnzi a korai elfogadkat, akik mg alacsonyabb korai rfolyam mellett jutnak bitcoinokhoz, gy segtve a rendszer sikerre vitelt. A korai elfogadknak ez a kedvezmnyezse szmos kritikt eredmnyezett, gyakran piramisjtkhoz hasonltva a rendszert, m a tmogatk szerint ez az sztnz szksges ahhoz, hogy a hlzat s az infrastruktra beinduljon, egy arnyosabb rszeseds nem ellenslyozn megfelelen azt a kockzatot amit egy j, nem tesztelt fizetsi rendszer hasznlata jelent.[5]

Mivel a tranzakcikat az egsz hlzat fel sztkldik a csompontok, azok teljesen nyilvnosak. Szemben a hagyomnyos pnzgyi intzetekkel, amelyek az gyfelek magnszfrjt a tranzakcikra vonatkoz informcik visszatartsval vdik, ezt a Bitcoin rendszerben az biztostja, hogy a cmek tulajdonosra vonatkoz informcik nem ismertek. Ha pldul Alz kld Bobnak 12 BTC sszeget, akkor a nyilvnos adatok kztt csak az ltszik, hogy kt cm kztt 12 BTC sszeg mozgott. Hacsak valamilyen oknl fogva a rsztvevk nem hozzk nyilvnossgra, hogy az adott cmeknek k a tulajdonosai, szinte lehetetlen ket sszekapcsolni. Ugyanakkor ha egy cmrl egyszer mr kiderlt, hogy kihez tartozik, az ahhoz tartoz korbbi tranzakcik is visszakereshetek.

A hlzaton s az elosztottan trolt adatbzisban a tranzakciknl a kifizet s a kedvezmnyezett kizrlag a bitcoincmvel jelenik meg. Ez a cm nem ms, mint egy kriptogrfiai kulcspr publikus fele, amely lehetv teszi a cm tulajdonosnak (aki a privt kulcsot egyedl birtokolja), hogy a cmn lv egyenleg terhre kiadott tranzakcikat alrja. Mivel egy szemly brmennyi cmet ltrehozhat magnak, amelyekrl nem derl ki, hogy egy emberhez tartoznak, a pnz mozgsnak kvetse szinte lehetetlen.

A hlzatot alkot csompontok kztt nincs kiemelt szerep, a jelenlegi megvalsts szerint mindegyikk a teljes adatbzist trolja, gy a rendszer brmekkora szm csompont kiesse esetn is tovbb mkdik.

Az anonimitst s a kzponti kontroll hinyt elnysnek tallhatjk az illeglis zletet folytatk is. A rendszerrel szembeni egyik leggyakoribb kritika szerint mkdse elsegti a trvnytelen zletek lebonyoltst, s emiatt az egsz fizetsi rendszert illeglisnak kell tekinteni.[6] A trvnyessgi agglyokra egy Bitcoint hasznl drogkeresked weblap irnytotta r a figyelmet.[7]

A Bitcoin protokoll a Nakamoto Satoshi cikkben[8] lert s ltala kzztett kliensben megvalstott elveket kveti.

A nyilvnos kulcs digitlis alrs segtsgvel lehetsg van ellenrizni, hogy egy adott cm tulajdonosa valban hozzjrult-e a cmhez tartoz egyenleg terhre trtn fizetshez. Az egyenleg ellenrzse az adott cmre korbban berkez, hasonlkppen alrt tranzakcik lekrdezsvel oldhat meg. A hlzatban rszt vev felhasznlk mindegyiknek van legalbb egy pnztrcja, amelyben helyben generlt nyilvnos-privt kulcsprok tallhatak. Tranzakci alrshoz a kliensprogram a privt kulcsot hasznlja. Fizets fogadshoz a nyilvnos kulcs egy olvashat formjt kell a msik flnek megadni. Ez az olvashat forma ltalban 33 krli szm karakterbl ll, s mindig egyessel kezddik, mint pldul 15VzdkAvVpZsVAhw84esj14GVXbzUm9VTk.

Az alapvet problma a fentiek biztostsa mellett annak megakadlyozsa, hogy valaki a birtokban lv pnzt tbbszr elkltse. Ennek megakadlyozsra az adatbzis 10 percenknt bvl egy-egy blokkal, ahol az j blokkot egy vletlenszeren vlasztott csompont lltja ssze nllan gy, hogy abban ne legyen tlklts. Az adatbzisba gy bekerlt blokkban szerepl tranzakcikat a tbbi csompont megtrtntnek fogadja el.

Mivel a kvetkez blokkot elllt rsztvev kivlasztsa vletlenszeren trtnik, elfordulhat, hogy tbb blokk jn ltre, egyes csompontok pedig a ksbbi blokkok ltrehozshoz nem ugyanazokat az elzmnyeket hasznljk. A hlzat tagjai az ltaluk elrhet blokkok kzl azokat fogadjk el rvnyesnek amelyekbl a leghosszabb lnc llthat el.

Annak rdekben, hogy ezt kihasznlva ne lehessen egy korbban mr elfogadott tranzakcit meg nem trtntt tenni, az j blokkok adatbzishoz adst a protokoll szndkosan nehzz teszi. A csompontoknak egy j blokk kzzttelekor bizonytaniuk kell, hogy jelents szmtsi teljestmnyt ignyl, nehz kriptogrfiai feladatot oldottak meg, ennek megkvetelt mrtke pedig folyamatosan gy van szablyozva, hogy a hlzaton krlbell 10 percenknt egy csompont legyen kpes ezt teljesteni. Ennek eredmnyeknt a hlzaton a tbbsgi dntst a mgttes szmtsi kapacits hatrozza meg. A hlzat feletti ellenrzs tvtelhez legalbb akkora szmtsi teljestmnyre van szksg, ami a hlzat tbb mint felt adja.

A szksges szmtsi teljestmny felajnlsnak sztnzsre minden egyes kzztett blokk utn a kzztev csompont rszesl az jonnan ltrejtt pnzbl, amelyet a sajt cmre rhat. Jelenleg minden blokkrt 25 Bitcoin jr, ez a ksbbiekben cskkenni fog, a protokoll ltal meghatrozott temben. Az gy kiosztott bitcoinok begyjtsre irnyul erfesztsek eredmnyeknt a hivatalos klienstl fggetlen clprogramok jttek ltre, amelyek kizrlagos clja a minl nagyobb szmtsi kapacits hlzatba kapcsolsa s gy ennek a jutalomnak az elnyerse. Ezt a folyamatot szoktk bnyszatnak (mining) nevezni, utalva arra, hogy a nemesfmek bnyszathoz hasonlan j rtkhordoz kerl forgalomba. Jelenleg a kapacits nagy rszt videkrtyk ltalnos cl processzorn fut clprogramok adjk.

Annak rdekben, hogy a 21 millis hatrhoz kzeledve is fenntarthat legyen az sztnzs, lehetsg van a tranzakcikhoz jutalk belltsra. Az egyes blokkokban szerepl tranzakcikhoz tartoz jutalkokat az adott blokkot kzztev node sajt cmre rhatja, gy sztnzve a blokkok ltrehozst. Ez azonban nem ktelez, jelenleg az tranzakcik nagy rsze jutalk nlkl trtnik.

Ahhoz hogy minden cmhez tartoz egyenleg ellenrizhet legyen, a korbbi tranzakcik mindegyikt trolni kell, gy az adatbzis mrete folyamatosan n. A mkdsi elv miatt legalbb nhny csompontnak trolnia kell a teljes adatbzist, de nem kell felttlenl az sszesnek. Jelenleg (2011 jnius) az adatbzis alig pr szz megabjt, gy minden kliens megkapja a teljes msolatot az els indts utn nem sokkal.

Nakamoto elkpzelse szerint ha az adatbzis nagyobb vlik, olyan kliensekre lesz szksg, amelyek az adatbzisnak csak a relevns rszt troljk. Erre a clra egy olyan Merkle fa szolgl, ami lehetv teszi, hogy a kliens az adatbzisnak olyan rszeit eldobja, amikrl tudja, hogy a jvben nem lesz r szksge, mikzben a megmarad rsz kriptogrfiai integritsa megmarad.

Az eredeti nylt forrskd kliens minden nagyobb platformra lefordtott vltozatban is elrhet, a bitcoinok kldshez s fogadshoz szksges minden funkcit tartalmaz, folyamatosan fejlesztik. A blokkok generlsra azonban csak a CPU hasznlatval kpes, GPU-alap generlshoz kln szoftver szksges.

A C++-ban rt kliensen kvl elrhetek ms kliensek is, a projekt kzponti oldaln az rdekldk ttekintst kaphatnak az elrhet alternatvkrl. Az jabb kliensek egy rsze nem ignyli a teljes blokklnc letltst, ehelyett egy tvoli gpen fut teljes bitcoin kliensre tmaszkodik, gy lnyegesen egyszerbben hasznlhat. (pl. Multibit, electrum)

A blokkok kzzttelhez szksges kriptogrfiai feladatok megoldsra klnll, nylt forrskd programok szolglnak, amelyek tbbsge a modern, programozhat grafikus hardvereket hasznlja a hlzat ltal ignyelt nehz kriptogrfiai feladat elvgzsre. Mivel a csompontok nagy szma miatt ma mr egy-egy felhasznlnak elenyszen kis eslye van egy blokkot megoldani s az rte jr jutalmat megszerezni, ezeket a programokat lehetsg van gy belltani, hogy egy szerver irnytsa alatt kzsen dolgozzanak. Ekkor ha az egyttmkd programok kzl egy megtallja a megoldst, a jutalmon osztoznak a rsztvevk.

A Bitcoin f fejlesztje Satoshi Nakamoto lnven publiklta a szoftvert. Ksbb Craig Steven Wright azt lltotta, hogy Satoshi,[9] de ksbb hitelt rdemlen nem tmasztotta ezt al. Sokig hittk, hogy Satoshi Nakamoto egy japn programoz, de ennek ellentmondott precz brit formai angolsga, amivel lerta a rendszert, s az amerikai szlengje, amivel frumozott, ami azt engedi felttelezni, hogy inkbb egy csoport ll a Bitcoin kibocstsa mgtt mintsem egy konkrt szemly. A Bitcoin szoftvert Satoshi Nakamoto eredetileg Windowsra rta csak meg, a linuxos vltozat ltrehozsban nagy szerepet jtszott Martti Malmi.

A legels blokkban az albbi zenet szerepel:

“The Times 03/Jan/2009 Chancellor on brink of second bailout for banks”

Ami magyar nyelvre sz szerint fordtva a kvetkezket jelenti:

“The Times 2009. janur 3., a pnzgyminiszter a hatrn van a bankok msodik kisegtsnek.”

Megoszlanak a vlemnyek arrl, hogy ez milyen cllal kerlt bele, egyesek szerint csupn idblyegz szerept tlti be (az els blokk a tovbbiakkal ellenttben rtelemszeren nem tud korbbiakra hivatkozni s gy bizonytani, hogy adott idpont utn jtt ltre), msok az zenetet a pnzgyi rendszer kritikjaknt vlik rtelmezni.

A bitcoint folyamatosan szmos kritika ri, jogi, gazdasgi, technolgiai megfontolsok alapjn egyarnt.

A nvnlklisg kivl terep a bnzk szmra: pnzmosshoz, nvtelen zsarolshoz hasznlhat, gyerekporn s illeglis hacker tevkenysg fizetsge lehet, br az amerikai szentus tagjai is megjegyeztk, hogy illeglis tevkenysg folytatshoz a kszpnz a leghatkonyabb fizet eszkz.

A kzponti rszablyozs hinya az rfolyamot nagyon vltozkonny teszi, a teljes monetris bzishoz kpest alacsony forgalom mellett mozg r pedig gyakran szlssges mozgsokat, hirtelen felfutsokat s drasztikus sszeomlsokat eredmnyez. Emiatt s a korai hasznlk ltal birtokolt nagy mennyisg bitcoin miatt szoktk piramisjtkhoz hasonltani a rendszert.

A tranzakcik visszafordthatatlansga egyes esetekben megnehezti a vsrlk tversekkel szembeni vdelmt, valamint a hagyomnyos banki rendszerekkel ellenttben ha valamilyen rosszindulat program eltulajdont bitcoinokat, azokat a hagyomnyos bankszmlkkal ellenttben eslytelen visszaszerezni. Ezt a kritikt azonban a rendszert hasznlk azon az alapon utastjk el, hogy a tradicionlis rendszerekben a kresemny utni kompenzci nem ingyenes, hanem be van ptve a pnzgyi szolgltatk zleti modelljbe. A bitcoin protocol bta, fejleszts alatt ll, tbbek kztt a beptett “escrow” funkci sem aktv mg.

A hlzat biztonsgt garantl s frissen kibocstott bitcoinokkal jutalmazott bnyszs 2013-ra jelents iparr ntt, az egymssal versenyz szereplk hatalmas szmtsi erforrsokat zemeltetnek. Ez hatalmas hardver- s energiaignnyel jr, ami sokak szerint flsleges s tlz trsadalmi kltsg egy fizetsi rendszer fenntartsrt. Ez a kritika sem felttlenl rendelkezik alappal, amg nincs rendelkezsre ll pontos adat a megszokott pnzgyi szolgltatk energia ignyrl, az egsz rendszert figyelembe vve (POS eszkzk, ATM-ek, banki pletek, stb). Ezekkel szemben a bitcoin rendszer llandan zemel, kzpontostatlan mivolta miatt nincs sznet a szolgltatsban.

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Bitcoin Wikipdia

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A group of Chinese investors has reportedly been defrauded after being pitched on a cryptocurrency launched in 2014 by a local UK government body.


Jan 14, 2016 at 17:45 | Stan Higgins

Two Florida law firms have filed a class action lawsuit in US district court against the digital currency exchange Cryptsy and its CEO, Paul Vernon.


Nov 30, 2015 at 22:50 | Pete Rizzo

Dogetipbot has announced it will go open-source just over one year after raising $445,000 from investors including Blackbird Ventures.


Sep 18, 2015 at 18:46 | Stan Higgins

A California politician has become embroiled in a growing controversy surrounding an altcoin and investors who say theyve been duped.

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What Is Bitcoin Cryptocurrency? Webopedia Definition


By Vangie Beal

Bitcoin is a digital payment currency that utilizes cryptocurrency (a digital medium of exchange) and peer-to-peer (P2P) technology to create and manage monetary transactions as opposed to a central authority. The open source Bitcoin P2P network creates the bitcoins and manages all the bitcoin transactions.

Often referred to as “cash for the Internet,” Bitcoin is one of several popular digital payment currencies along with Litecoin, Peercoin and Namecoin. When the word Bitcoin is capitalized, it usually refers to the software and systems used for bitcoin (in lowercase it means the actual currency).

Bitcoin is considered the biggest cryptocurrency. It was first introduced in 2009 and is the most widely-traded cryptocurrency. Bitcoin as an implementation of the cryptocurrency concept was described by Wei Dai in 1998 on the cypherpunks mailing list. Dai suggested a new form of money that uses cryptography to control its creation and transactions, rather than a central authority. In 2009, the Bitcoin specification and proof of concept was published in a cryptography mailing list by Satoshi Nakamoto. As noted in the Official Bitcoin FAQ, Satoshi Nakamoto left the project in late 2010 without revealing much about himself.

Payments are made via a Bitcoin wallet application that resides on a user’s computer or mobile device, and a person only needs to enter the recipient’s Bitcoin address information and payment amount before pressing send to complete payment.

New bitcoins are created by a competitive and decentralized process called “mining”. Bitcoin miners are processing transactions and securing the network using specialized hardware and are collecting new bitcoins in exchange. The Bitcoin protocol ensures new bitcoins are created at a fixed rate, making the process of bitcoin mining a very competitive business.

According to eWeek, efforts to improve Bitcoin mining are now under way, working under the basic assumption that the cheaper you can mine Bitcoins, the more money you can make.

While attackers are going after Bitcoin-related sites, there is an important distinction between the security of the Bitcoin network and the Bitcoin exchanges. According to, no one has ever found a critical vulnerability within the Bitcoin protocol itself that would allow a user within the Bitcoin network to fraudulently create coins or forge transactions. That said, there have been compromises of various Bitcoin exchanges throughout the virtual currency’s lifetime, and as the value of a Bitcoin increases, so does the risk in using exchanges.


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My New Best Bitcoin (and altcoin) Wallet Exodus Wallet …

Its been a while since I reviewed Bitcoin wallets. The reason for this is that most Bitcoin wallets are basically the same so rarely do you stumble upon a wallet that is innovative.

Until today

A few days ago I got an email from one of my subscribers telling me he didnt take my advice for the best Bitcoin wallet and used the Exodus wallet instead. He then went on to glorify the wallets interface and ease of use. I wasnt aware of such a wallet so I looked it up online and apparently Exodus is indeed a new Bitcoin wallet.

Before going any further watch this video and see for yourself why its so unique.

Exodus seemed to have been launched a month ago (July 2016) and still hasnt gained enough reputation in the Bitcoin community. Actually Exodus is not just a Bitcoin wallet, its a Blockchain assets wallet. This means you can store Bitcoins, Litecoins, Dash, Ether and Dogecoins on Exodus all together.

But this is not all that makes Exodus so unique, here are the main things that I found so appealing:

Probably the strongest suite Exodus has is its user interface. Even if I didnt know nothing at all about Bitcoin or cryptocurrencies I would still be able to use this wallet. It reminds me of Circle in the simplicity. Exodus is the kind of product you fall in love with the first time you use it, and thats quite rare inthe cryptocurrency world.

Heres how an overview of your blockchain assets looks like:

Nice huh? :)

Since Exodus is a desktop wallet navigation is fast and the private keys to your cryptocurrencies are stored on your machine. Exodus is a litewallet so you dont need to download the whole Blockchain to your computer like you do with Bitcoin Core. Exodus is currently compatible with Mac, Windows and Linux. If you need to back up your wallet theres a VERY simple step by step wizard built in inside the wallet that will help you do so.

You will also receive a backup link via email if you want to install Exodus on a another machine (say your computer gets destroyed). Its all very secure through the use of a password and a mnemonic phrase (in case you forget your password).

One of the best features of Exodus in my opinion is the ability to trade your altcoins for Bitcoin and vice versa. Exodus has a built in exchange (powered by Shapeshift) that allows you to trade cryptocurrencies in seconds. You cant buy coins with fiat, but since the whole idea of Exodus is to move away from any verification processes and dealing with banks I think that fits in perfectly.

Its OKto make a crappy product, its not OK to leave it that way. I think what got my attention the most is the genuine interest Exodus founders had in their users opinion. Of course they are only about a month into running this project but something tells me JP and Daniel (the founders) are here to stay. You can see it in the simple to understand support videos theyve uploaded, the multiple communication channels theyve supplied on their site and the direct messaging platform to the foundersvia Slack.

To sum things up, Exodus looks like a complete hit. The only downside I can see at the moment is the fact that the company and wallet havent gained enough reputation yet. Combine that with the fact that the Exodus code isnt open source and you will always arouse some suspicion from the crypto community. Also, in order to become a true killer app the developer will have to continue and expand to mobile as well in my opinion.

But I believe that as time goes by and more early adopters come on board Exodus will quickly gain its loyal user base.

Click here to check out Exodus for yourself

If youve had any experience with the Exodus wallet Id love to hear about it in the comment section below.

altcoin Wallet Exodus Wallet Review”>

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Blogger and owner of 99Bitcoins. I’ve been dealing with Bitcoin since the beginning of 2013 and it taught me a lesson in finance that I couldn’t get anywhere else on the planet. I’m not a techie, I don’t understand “Hashes” and “Protocols”, I designed this website with people like myself in mind. My expertise is online marketing and I’ve dedicated a large portion of 99Bitcoins to Bitcoin marketing.

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Bitcoin – Wikipedia, den frie encyklopdi

Bitcoin (valutaforkortelse: BTC eller XBT) er et online betalingssystem og en virtuel valuta, der kan bruges til betalinger et begrnset antal steder p internettet. Det blev opfundet af Satoshi Nakamoto, som offentliggjorde sin opfindelse i 2008 og efterflgende udgav systemet som open source i 2009. Systemet er peer-to-peer, s brugere kan indg i transaktioner med hinanden uden mellemled som pengeinstitutter eller centralbanker. Skabelsen af nye bitcoin og godkendelsen af transaktioner bliver i bitcoin-systemet hndteret kollektivt i et netvrk af computere ved hjlp af kryptografiske algoritmer. Som flge heraf er bitcoin i modstning til traditionelle valutaer hverken reguleret eller underlagt beskyttelsesregler i lovgivningen p dansk og europisk plan.[1] Nye bitcoin skabes i et netvrk p internettet, som er tilgngeligt for alle, via en proces kaldet minedrift (mining).

Bitcoin blev opfundet af Satoshi Nakamoto, som udgav en artikel den 31. oktober 2008 med titlen “Bitcoin: A Peer-to-Peer Electronic Cash system”. Systemet, der bygger videre p flere tidligere ider, blev udgivet som open source i januar 2009. Bitcoin er en af de frste kryptovalutaer efter forgngere som David Chaums ecash, der havde sin frste transaktion i 1994, og OpenCoin, som nu hedder Ripple, der havde programmel fr november 2008.

Den frste til at modtage bitcoin var programmren Hal Finney, som tidligere havde skabt et lignende system kaldet RPOW. Finney hentede softwaren p bningsdagen og modtog 10 BTC fra Satoshi Nakamoto. Blandt andre tidlige tilhngere var Wei Dai, skaberen af forgngeren b-money, og Nick Szabo, skaberen af forgngeren bit gold. Der har vret megen spekulation om, hvorvidt Satoshi Nakamoto i virkeligheden var en af disse personer. Det skaldte hashcash-system, som bitcoin anvender, blev foreslet af Adam Back i 1997.

Processen, der udvinder nye bitcoin samt regler og formater for transaktioner med den digitale valuta, er beskrevet i den skaldte Bitcoin Protocol. Protokollen opdateres og ndres lbende af udviklere, og den anvendes i et skaldt peer-to-peer-netvrkskonfiguration, dvs. et decentralt datanet, hvor hver computer i datanettet har lige stort ansvar for datanettets funktionalitet.

For at kunne modtage og betale med bitcoin, skal man have en skaldt pengepung (wallet) installeret p sin computer. Pengepungen implementerer ofte peer-to-peer protokollen og er afhngig af netvrket for at fungere. Pengepungen er et program, der giver adgang til en rkke adresser med hver deres saldo i bitcoin. En pengepung kan ogs ligge hos forskellige udbydere, hvilket kan sammenlignes med at have penge stende i banken.[1] Alle bitcoin-transaktioner er offentlige og foregr alene mellem to parter ved udveksling af beskeder underskrevet med digitale signaturer, men det er muligt for udbydere at have interne konti og transaktioner som bitcoin-netvrket aldrig ser.

En bitcoin-adresse er p 27-34 tegn, og bestr bde af bogstaver og tal som f.eks. 1HB5XMLmzFVj8ALj6mfBsbifRoD4miY36v. Hvis en bruger nsker at betale med bitcoin, er det ndvendigt at kende betalingsmodtagerens adresse. Overfrslen foregr fra brugerens pengepung, hvorfra transaktionen sendes til verificering i netvrket. Da bitcoin er uden central autoritet, er det op til den enkelte bruger at bestemme, hvor mange verificeringer der skal til, fr transaktionen anses for afsluttet.

Alle pengetransaktioner er offentlige og foregr alene mellem to parter ved udveksling af beskeder underskrevet med digitale signaturer. Man skal holde forbindelsen mellem sin adresse og sin identitet hemmelig, hvis man vil bruge bitcoin anonymt. For at gre bitcoin svrere at spore, kan man forvanske deres oprindelse ved at sende dem til en adresse, som modtager fra mange mennesker. Derefter blandes de modtagne bitcoin tilfldigt og distribueres igen. Dette blandingsaggregat kaldes p engelsk en tumbler (en blander). Den kendsgerning, at man ikke ndvendigvis kan knytte adressen, som har modtaget bitcoin, sammen med ejeren af adressen, medfrer, at bitcoin kan vre attraktiv til nogle kriminelle forml. Bitcoin er derfor nogle gange blevet sat i forbindelse med illegale aktiviteter som f.eks. det sorte online-marked Silk Road.[1]

Valutaen skabes og uddeles til brugerne i praksis tilfldigt, men under anvendelse af vsentlige beregningsressourcer skaldt minedrift (mining). Jo mere minedrift man driver, desto hjere bliver chancen for, at man fr gevinst, se afsnittet om indsatsbeviskden forneden. Mngden af nye bitcoin, der skabes, aftager med tiden. Sledes har systemet en endelig forudbestemt pengemngde (21 millioner). Pengemngden vokser som en geometrisk rkke hver 210.000. blok (omtrent hvert 4. r); i 2013 vil halvdelen vre genereret, og i 2017 vil 3/4 vre genereret.

Pengepunge kan man generere selv, og det er derfor let at skille foretagender fra hinanden.

Med sin forudbestemte og endelige pengemngde er systemet baseret p en deflationskonomi. Stigende eftersprgsel efter penge kan alene dkkes af stigende vrdi per enhed af valutaen. Og systemet er derfor ogs designet til at brugerne kan dele valutaen op i mindre enheder helt ned til 8. betydende ciffer. Den mindste enhed kaldes en “satoshi”. Det har derfor kun psykologisk betydning, at n bitcoin kan koste tusindvis af kroner: 1.000.000 re er det samme som 10 tusindkronesedler.

Bitcoin-systemets relative succes har frt til fremkomsten af en rkke lignende kryptovalutaer med navne som Litecoin, Peercoin, Dogecoin, Namecoin, Mastercoin og Primecoin. Samtidig vurderer nogle, at det er nogle helt srlige mindre grupper, der tiltrkkes af bitcoin som betalingsmiddel: Teknologientusiaster, der fascineres af de nye digitale muligheder, professionelle spekulanter, der opkber og gemmer bitcoin for at tjene penge, ideologisk orienterede anarkistisk-liberale, der tiltrkkes af ideen om en ikke-statslig betalingsenhed, samt grupper, der nsker at frdes og handle p nettet uden overvgning, herunder ogs kriminelle.[2]

Det danske Finanstilsyn og Den europiske banktilsynsmyndighed EBA har advaret mod brug og handel med bitcoin. Finanstilsynet anser ikke bitcoin for omfattet af den finansielle lovgivning.[3]

Fremkomsten af bitcoin og andre former for digitale valutaer har fet en rkke konomer til at interessere sig for fnomenet. Vurderingen er dog ofte skeptisk eller direkte negativ.[4]Nobelpristageren i konomi Paul Krugman har sledes i et bermt blogindlg “Bitcoin Is Evil” fremfrt, at en valuta for at fungere ordentligt bde skal kunne fungere som et betalingsmiddel og som et stabilt vrdiopbevaringsmiddel, og at bitcoin vil f svrt ved at opfylde det sidste kriterium, fordi der ikke er nogen centralbank eller offentlig myndighed til at garantere vrdien.[5] konomiprofessor ved University of California, Berkeley Brad DeLong mener, at bitcoin aldrig kan blive et alment accepteret betalingsmiddel, fordi omkostningerne ved at skabe en bitcoin-klon som Dogecoin o.l. med stort set de samme egenskaber er meget sm og den konomiske tilskyndelse til at gre det vil vre meget stor, hvis bitcoin fr en vsentlig udbredelse.[6] Professor Tyler Cowen argumenterer, at en deflationr konomi, hvor priserne konstant falder, som bitcoin er designet til at skabe i det lange lb, vil vre problematisk.[7]

Ogs Danmarks Nationalbank har undersgt fnomenet bitcoin i bankens kvartalsoversigt i 1. kvartal 2014.[1] Analysen nvner, at betalinger med bitcoin sammenlignet med andre betalingsformidlingssystemer har lave transaktionsgebyrer, men peger p en rkke uhensigtsmssigheder ved bitcoin som betalingsmiddel: De kan kun anvendes f steder, kbekraften er meget svingende som flge af de kraftige kursudsving p bitcoin, systemet bygger p en underliggende deflationstendens, anvendelsen er ikke dkket – og derfor heller ikke beskyttet – af lovgivning, f.eks. ved hacker-angreb, og mange mennesker vil formodentlig mene, at betalingen i praksis foregr mere besvrligt end ved gngse betalingsmetoder. Derudover mener analysens forfattere, at det vil vre vanskeligt at holde omkostningerne ved at benytte bitcoin nede, idet det ligger i metodens konstruktion, at det bliver mere og mere omkostningsfuldt at skabe nye bitcoin. Disse omkostninger skal i sagens natur dkkes ind.[1]

Indsatsbevis-algoritmen, der udsteder nye bitcoin, er en vigtig del af Bitcoin. Hver mntenheds skiftende ejerskab registreres ved hjlp af digitale signaturer. Denne registrering sker i blokkden (se forneden), og er den eneste offentligt tilgngelige information om Bitcoin. Navne og adresser er sledes ikke gemt i blokkden, som gemmer alle transaktioner.

Registreringer af aktuelle bitcoin-transaktioner, der er kendt som en blok, tilfjes til fortegnelse over tidligere transaktioner i blokkden (block chain).

Adressen er afledt af den offentlige ngle (public key) til pengepungen. Adressen gengives med grundtallet (radix) 58 for p den mde at gre adresserne kortere, end hvis der blev brugt f.eks. decimal- eller hexadecimal-gengivelse.

For at f en transaktion distribueret i systemet skal man i praksis betale et transaktionsgebyr. Transaktionsgebyret fr minedriveren som belnning for at inkludere transaktionen i den nye blok, der blev fundet. Transaktionsgebyret kaldes ogs minedriverens afgift (miner’s fee).

Den asymmetriske krypteringsalgorithme som Bitcoin bruger, er Elliptic Curve DSA, som bygger p, at det er for svrt at finde den diskrete logaritme af et tilfldigt elliptisk kurveelement (fra en stor elliptisk kurve) ud fra et offentlig kendt basispunkt.

Grundlaget for bitcoins transaktionsmekanisme er indsatsbevis-algoritmen. Som indsatsbevis-algoritme (proof-of-work algorithm), bruges hashcash-konceptet, i inkarnation som SHA-256. Da SHA-hashen er kryptografisk plidelig, kendes intet system for, hvordan man hurtigt finder data som hasher til en given vrdi, derfor anses bitcoins for at blive tilfldigt tildelt. Netvrket accepterer kun hashes, som er tilpas lave (i hexadecimalgengivelsen vil de have flere nuller foran). For at finde en sdan hash, stter minedriveren sin datamat til at hashe tilfldig data. Denne proces kaldes minedrift. Netvrket justerer svrhedsgraden (antal nullerne) i henhold til omfanget af minedriften.

Indsatsbevis-algoritmen, kombineret med blokkden, lser et gammelt datalogisk problem: problemet om byzantinsk fejltolerance:

Indsatsbevis-algoritmen er en lsning p de byzantinske generalers problem. Jeg vil hermed forsge at genformulere det i den kontekst.

Et antal byzantinske generaler har alle computere, og vil gtte kongens wi-fi-kodeord ved brug af et brute-force-angreb. De ved, at kodeordet bestr af et givent antal tegn. S snart de stimulerer netvrket til at generere en pakke, skal de gtte kodeordet p begrnset tid, for at bryde ind og slette deres spor, ellers bliver de opdaget og kommer i knibe. De har kun nok processorkraft til at knkke det hurtigt nok, hvis et flertal af dem angriber p samme tid.

De er ligeglade med, hvornr angrebet finder sted, bare de alle er enige. Det besluttes at enhver kan bestemme et tidspunkt, og det frste tidspunkt der bliver udmeldt, vil vre det officielle angrebstidspunkt. Problemet bestr i at netvrket ikke leverer meddelelser omgende, og hvis to generaler udmelder forskellige angrebstidspunkter nsten samtidigt, vil nogle f den ene udmelding frst, og andre vil f den anden frst.

De bruger en indsatsbeviskde til at lse problemet. S snart hver general modtager det angrebstidspunkt han hrer frst, stter han sin computer til at lse et ekstremt svrt indsatsbevis-problem som hasher angrebstidspunktet. Indsatsbevis-algoritmen er s svr, at det forventes at tage dem 10 minutter, selv nr de arbejder samtidigt (men uafhngigt), fr nogen finder en lsning. S snart en af generalerne har fundet et indsatsbevis, udmelder han det til netvrket, og alle ndrer deres nuvrende indsatsbevis-beregnelse til at inkludere dette indsatsbevis i det hash de regner p. Hvis nogen arbejdede p et andet angrebstidspunkt, skifter de til dette, fordi dets indsatsbeviskde nu er lngere.

Indsatsbeviskden kan gemmes effektivt i et Merkle tr.

Hvis svrhedsgraden er hj, kan det tage lang tid at finde en blok. Blokkene belnnes med flere bitcoin (som kan vre flere tusinde kroner). Derfor slr folk sig sammen i mineforbund (mining pools). P den mde fr alle hyppigt en lille gevinst, da der oftere vil vre nogen i netvrket der finder en blok. Mineforbundet krver naturligvis, at man yder sin andel for at f del i udbyttet.

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Blockchain-Based Gold Settlement is Coming to London …

Fintech company Paxos has partnered with the Euroclear team to bring blockchain-based gold settlement to the London Bullion Market. The project, called Euroclear Bankchain, aims to leverage blockchain technology to make post-trade settlement more efficient.

Also read:Top 10 Killer Apps for Bitcoin: Ideas That Can Change the World

Paxos and Euroclear executives announced the collaboration during this weeks SIBOS annual conference in Geneva, Switzerland. Paxos CEO Charles Cascarilla told attendees the partnership will producethe first concrete blockchain use case for gold settlement in the London Bullion Market.

The blockchain-based gold solution will benefit investors and key stakeholders during the Bankchain initial offering, Cascarillatold reporters.

We are coming to market with a ground-breaking offering that will drastically impact the post-trade process and overall trading infrastructure within the global gold market.

Founders Richmond Teo and Charles Cascarilla consider the flagship product Bankchain to be a next-generation blockchain settlement platform. The platform providesprompt settlement and automationto bringmore fluid efficiency to post-trade capital markets, Cascarilla added.

The company has raised a total of $28.25 million USD through two funding rounds. Last year, withinvestors such as the Digital Currency GroupandBlockchain Capital, the company acquired $25 million in one Series A funding round. Cascarilla and partners first launched Bankchain under the cryptocurrency exchange itBits umbrella.

Euroclear claims it has a reputation as a trusted post-trade services provider witha double-A rating from Standard & Poors.

The companyworksto provide settlement and safekeeping for securities, equities, bonds, and derivatives to investment funds. Italso believes blockchain technology can transform the post-trade markets.

Currently, post-trade settlements often take days and come with significant costs from third parties, auditors, and paperwork. Euroclear says that with a distributed ledger mechanism, clearing can be done faster, more formally, and with cost savings. The Bankchain protocol, it says, can advance settlement times by providinga more frictionless environment.

As a neutral market infrastructure, with a track record of providing high quality, reliable post-trade services to some of the worlds leading financial institutions, we are adopting a collaborative approach wherever possible, working with third-party innovators in ways that reward their innovation while simultaneously giving us flexibility, said Luc Vantomme, Euroclears managing director and Global Head of Innovation.

The settlement of unallocated gold is a very capital-intensive process. We are working to develop a service to reduce risk and balance sheet constraints.

Both firms believe Bankchain can produce better results than the traditional London Bullion Market system. Cascarilla said that overall, the platform will reduce counterparty risk, and offer real-time tracking and transparent auditability.

The advent of blockchain settlement platforms, he said, will streamline the post-trade process. To prove its worth, his companyis startingwith the London Bullion and precious metals markets.

What do you think about Pax and Euroclears blockchain-based gold settlement Bankchain? Let us know in the comments below.

Source: Paxos

Images via Shutterstock, Pixabay.

Did you know is throwing a blockchain conference in London this year? Our premiere event,Blockchain: Money,features the biggest innovators and executives in the industry. The event will also take placein the beautiful surroundings of 155 Bishopsgate, London onNovember 6-7, 2016. Reserve your tickets today!

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Cloud Services – AT&T Enterprise Business

Creating a coherent cloud strategy is a struggle for many organizations. Often, the rush to gain a competitive advantage by adopting innovative technologies leads to hurried decisions that dont take into account all the performance and security issues. Figuring out how to connect different cloud applications and vendors is also a major challenge and every organization has to come up with the strategy that fits its unique needs and business goals.

With AT&T global network offerings, you can optimize computing, storage, software, development and even network resources in a cloud-based environment. We offer end-to-end delivery capacity on a global scale, backed by decades of experience and trusted expertise. Together with our extensive service provider ecosystem, we provide a huge breadth of cloud, security, and networking capabilities. All through a single point of contact.

Whether you want to take advantage of specific capabilities or completely outsource your cloud infrastructure, we can help.

Learn more about AT&T Cloud Services >

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