nettle: Cipher modes
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1 6.3 Cipher modes
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1 Cipher modes of operation specifies the procedure to use when encrypting
1 a message that is larger than the cipher’s block size. As explained in
1 ⇒Cipher functions, splitting the message into blocks and
1 processing them independently with the block cipher (Electronic Code
1 Book mode, ECB), leaks information.
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1 Besides ECB, Nettle provides several other modes of operation: Cipher
1 Block Chaining (CBC), Counter mode (CTR), Cipher Feedback (CFB) and a
1 couple of AEAD modes (⇒Authenticated encryption). CBC is widely
1 used, but there are a few subtle issues of information leakage, see,
1 e.g., SSH CBC vulnerability (http://www.kb.cert.org/vuls/id/958563).
1 Today, CTR is usually preferred over CBC.
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1 Modes like CBC, CTR and CFB provide _no_ message authentication, and
1 should always be used together with a MAC (⇒Keyed hash functions)
1 or signature to authenticate the message.
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