Cristina Nita-Rotaru wrote:
> 
> Hello.
> 
> There might be a problem with EVP_DecryptUpdate.
> 
> My understanding was that EVP_EncryptUpdate can be called
> multiple times and then conclude the encryption by calling
> EVP_EncryptFinal. A similar mechanism applies for
> EVP_DecryptUpdate and EVP_DecryptFinal.
> 
> In a test that I am running where two blocks of 16 bytes
> are encrypted by calling EVP_EncryptUpdate twice (each on 16 bytes)
> and then EVP_EncryptFinal, when I want to perform the
> decryption in a similar manner, the first call of EVP_DecryptUpdate
> on the first 16 bytes reports that only 8 bytes where decrypted.
> Shouldn't this be 16?
> 

I've recently answered this in more detail in openssl-users. No its not
a bug because the decrypt routines have to store up to one block of
decrypted data internally due to the padding checking.

Steve.
-- 
Dr Stephen N. Henson.   http://www.drh-consultancy.demon.co.uk/
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