From: Stephen Sprunk <[EMAIL PROTECTED]>
stephen> Can someone help me implement the EVP macros for AES 128-bit CFB and
stephen> OFB modes? It's too messy for me to figure out.
stephen>
stephen> I've got non-EVP versions written, but it appears the EVP macros do
stephen> their own implementation of the various modes and only call the base
stephen> ECB function.
Nope, they don't do their own implementation, all they do is write EVP
wrappers that call the different functions of the algorithm itself.
Note that this puts a requirement on the algorithm functions to follow
a certain name standard. The expected frunctions are, for a certain
{prefix} (AES in the AES case, I assume :-)):
{prefix}_ecb_encrypt
{prefix}_cbc_encrypt
{prefix}_ofb64_encrypt
{prefix}_cfb64_encrypt
Furthermore, there are a few semantic things. All of those functions
have to use the exact same arguments for all algorithms, except for
the key schedule argument. Also, {prefix}_ecb_encrypt is expected to
encrypt only one block, while the others are expected to encrypt the
whole message that is sent to them.
stephen> I've also got a trial implementation of CTR mode, but I don't
stephen> see where that would fit into EVP or the ASN.1 stuff.
I don't think CTR is considered at all in the EVP layer. In other
words, you may implement it, but it will only be available as a direct
algorithm function, not as part of the EVP layer.
In any case, I can most certainly help you out, as I've already
fiddled with the first patches you sent.
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