botan

Botan is a crypto library written in C++. It provides a variety of
cryptographic algorithms, including common ones such as AES, MD5, SHA,
HMAC, RSA, Diffie-Hellman, DSA, and ECDSA, as well as many others that
are more obscure or specialized. It also offers X.509v3 certificates
and CRLs, and PKCS #10 certificate requests. A message processing
system that uses a filter/pipeline metaphor allows for many common
cryptographic tasks to be completed with just a few lines of code.
Assembly optimizations for common CPUs, including x86, x86-64, and
PowerPC, offers further speedups for critical tasks such as SHA-1
hashing and multiple precision integer operations.

Botan is licensed under the same permissive terms as FreeBSD itself.