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When a bit error happens in an IV, what would the result of decrypting a cipher-text be in the different encryption modes like ECB, CBC, CFB, OFB, and CTR?

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migrated from stackoverflow.com Oct 30 '12 at 22:58

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This seems a strange question to ask. Is it for an assignment or are you trying to select the best mode for a particular application? Regardless:

  1. ECB does not use an IV.

  2. CTR has a nonce value, which could be considered an IV. A bit error there will produce an entirely different key stream for every block.

  3. CBC and CFB will corrupt the first plaintext block, but thereafter it is OK.

  4. In the case of OFB, I believe the entire plaintext will be corrupted because the entire stream of data is determined by the IV (plus the key, of course).

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CTR does use an IV (the nonce), and a bit error there will produce an entirely different key stream for every block. –  mfanto Oct 30 '12 at 20:14
    
@mfanto I've edited my answer to include that, thanks. –  Duncan Jones Oct 30 '12 at 20:50
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