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kokke / tiny-AES-c

Small portable AES128/192/256 in C
The Unlicense
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Storing IV after encryption #200

Closed Tardymo closed 2 years ago

Tardymo commented 2 years ago

https://github.com/kokke/tiny-AES-c/blob/12e7744b4919e9d55de75b7ab566326a1c8e7a67/aes.c#L513

Is storing of IV really necessary at the end of AES_CBC_encrypt_buffer? My use case requires the same IV for each encryption, so now I must call AES_ctx_set_iv each time. There are two unnecessary memcpy calls then. Sure I can comment the line out, but maybe you could add an #ifder configuration macro for this?

jmons commented 2 years ago

I think, and I could be wrong, but what you're defining here isn't CBC mode, which this function implements? But instead, you should perhaps, wrap around ECB mode with your own IV manipulation?

kokke commented 2 years ago

Hi @Tardymo :)

I agree with what @jmons says: It sounds like you're doing something other than CBC?

See https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_block_chaining_(CBC)

The IV should be updated between each block. That is the reason for the memcpy-call.