[Cryptography] CFB/OFB/CTR mode with HMAC for key stream

Memory Vandal memvandal at gmail.com
Mon May 1 03:07:39 EDT 2017

Hello List,

I was wondering if using HMAC with something like SHA-256 to create a key
stream in CFB/OFB/CTR mode is a bad idea.

Considering that in CFB/OFB/CTR modes, the cipher required in the mode is
used only to perform encryption operation for both encryption and
decryption, a HMAC can be used to generate a key stream.

So, the overall CFB/OFB/CTR mode remains exactly same with exception of
using HMAC in place for a cipher. The key being used as HMAC key while IV
can be as the HMAC message.

I am not a cryptographer but, have some experience with implementing
cryptography. I could not come up with reasons as to why this could be a
bad idea.


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