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Convergent encryption, also known as content hash keying, is a cryptosystem that produces identical ciphertext from identical plaintext files. This has applications in cloud computing to remove duplicate files from storage without the provider having access to the encryption keys.〔Secure Data Deduplication, Mark W. Storer Kevin Greenan Darrell D. E. Long Ethan L. Miller http://www.ssrc.ucsc.edu/Papers/storer-storagess08.pdf〕 The combination of deduplication and convergent encryption was described in a backup system patent filed by Stac Electronics in 1995.〔System for backing up files from disk volumes on multiple nodes of a computer network, US Patent 5,778,395 filed October 1995, http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5778395.PN.&OS=PN/5778395&RS=PN/5778395〕 This combination has been used by Farsite,〔Reclaiming Space from Duplicate Files in a Serverless Distributed File System, MSR-TR-2002-30, http://research.microsoft.com/apps/pubs/default.aspx?id=69954〕 Permabit,〔Data repository and method for promoting network storage of data, US Patent 7,412,462 provisionally filed Feb 2000, http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7,412,462.PN.&OS=PN/7,412,462&RS=PN/7,412,462〕 Freenet, MojoNation, GNUnet, flud, and the Tahoe Least-Authority File Store.〔Drew Perttula and Attacks on Convergent Encryption https://tahoe-lafs.org/hacktahoelafs/drew_perttula.html〕 The system gained additional visibility in 2011 when cloud storage provider Bitcasa announced they were using convergent encryption to enable de-duplication of data in their cloud storage service.〔Finally! Bitcasa CEO Explains How The Encryption Works, September 18th, 2011, http://techcrunch.com/2011/09/18/bitcasa-explains-encryption/〕 == Overview == # The system computes the cryptographic hash of the plaintext in question. # The system then encrypts the plaintext by using its hash as a key. # Finally, the hash itself is stored, encrypted with a key chosen by the user. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Convergent encryption」の詳細全文を読む スポンサード リンク
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