Hello Billy,
On 23.04.2020 04:36, Billy Brumley wrote:
I'm tasked to implement certain cryptographic functions (chiefly
signature creation/validation) using the SM2 algorithm for a
communication testing application. My problem is that the standard which
I need to follow (which is, unfortunately, not a public standard) states
that the signature needs to be generated over H(data input) || H(some
ID) , so I cannot use the EVP-Method as I understand it from
https://www.openssl.org/docs/manmaster/man7/SM2.html (here, H is the SM3
hash function). This would be possible to achieve by generating the
digest and then using the (albeit deprecated) function ECDSA_do_sign for
ECDSA but I don't know how to do it for SM2.
It seems like you're trying to roll your own SM2 -- don't do that ;)
No, actually I don't. But tell that the standards groups ;-)
Is there any way to do this with openssl? Any help or pointer is very
much appreciated!
I ... think it is possible directly with EVP and control strings. Step through
openssl pkeyutl -inkey private.key -in /some/file -rawin -sign
-pkeyopt sm2_id:foobar
in a debugger and that should get you on the right path.
BBB
thanks for the pointer! This got me started in the right direction. I
did not use the debugger, but the source code of pkeyutil instead ;-)
I can now (I hope) generate signatures without using the built-in digest
hash first, by simply calling
EVP_DigestSignInit(mctx, NULL, NULL, NULL, pkey)
instead of
EVP_DigestSignInit(mctx, NULL, EVP_sm3(), NULL, pkey)
Thank you again and stay well,
Jörg
--
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