On 10/31/11 13:43, Huie-Ying Lee wrote:
Hi,
I have a couple of questions regarding the EVP_MD_CTX_copy_ex()
function in crypto/evp/digest.c and I would appreciate if you can shed
some light upon it.
Q1: If a digest copy function is provided by an engine, is the
EVP_MD_CTX_copy_ex() function the only function in OpenSSL that will
call that digest copy function ?
Q2: If an engine uses the digest context passed from the OpenSSL's
EVP_* functions directly, then the direct memcpy() in the
EVP_MD_CTX_copy_ex() function does the copy, and therefore, the engine
shouldn't need to do this copy again. Because the direct memcpy() is
sufficient for the copy, it appears to be unnecessary for the engine
to provide a copy function. Is this the case ?
Thanks,
Huie-Ying Lee
Hi,
Regarding the previous two questions that I asked on this alias, I have
determined that:
1) If a digest copy fucntion is provided by an engine, then the
EVP_MD_CTX_copy_ex() function is the only function in OpenSSL that will
call that digest copy function.
2) It is not necessary for an engine to provide a digest copy function,
if this engine uses the context passed from upper EVP functions directly.
Moreover, I found an existing engine example that doesn't provide a
digest copy function in its sha1 support. This existing engine is the
Intel Accelerator OpenSSL Engine (intel-accel-1.4.tar.gz) and it can be
found in the OpenSSL Contribution list (http://www.openssl.org/contrib).
If anybody has different understanding of these issues, could you please
let me know ?
Thanks,
Huie-Ying Lee
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