How did I break this signature library?

Sage Gerard sage at
Mon Jun 28 03:44:11 UTC 2021

Hi all,


I compile this small EVP program into a dynamic library, in which
libcrypto is statically linked. A nearby Racket program needs this
dynamic library for a foreign function interface. I do things in an odd
order, but I am able to create and verify signatures with this setup.

Let's say the library's output signature is in file.sha1.sig, and the
signature was created using the unencoded SHA-1 digest in file.sha1. I
would compare verification output using my host 1.1.1f binary using:

$ <file.sha1 openssl pkeyutl -sign -verify -pubin -inkey public.pem
-sigfile file.sha1.sig

Signature verification fails, so I made a mistake. I'm confused because
the program still (broadly) follows the wiki, and it verifies its own
valid-looking signatures successfully.

Can the library and binary disagree because of different OpenSSL
versions? If not, what did I do to make them produce different output
for the same CHF and keypair?


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