On May 21, 7:37 pm, glauberyt <[email protected]> wrote:
> Hello!
> I have a question: how to set the length of chaining block (CBC, CFB, OFB,
> ECB etc.) for AES in Crypto++? I thought it is taken from the length of init
> vector, but it isn't.
Some modes require the chaining size to be that of the underlying
block cipher's block size. For example, trying to set the feedback or
chaining size for CBC mode will result in an exception (if I recall
correctly).

For modes which accept a size, I believe you need to use an external
mode cipher. For example:
AESEncryption aes(...);
CFB_Mode_ExternalCipher cfb(aes, ..., <feedback size>);

There is also a SetFeedbackSize which can be used on the external mode
cipher objects. You can cruise the class reference to locate objects
of interest (such as CFB_Mode_ExternalCipher) at
http://www.cryptopp.com/docs/ref/annotated.html.

Jeff

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