Crypt::RSA is a pure-perl, cleanroom implementation of the RSA public-key
cryptosystem. It uses Math::Pari(3), a perl interface to the blazingly fast
PARI library, for big integer arithmetic and number theoretic computations.

Crypt::RSA provides arbitrary size key-pair generation, plaintext-aware
encryption (OAEP) and digital signatures with appendix (PSS). For
compatibility with SSLv3, RSAREF2, PGP and other applications that follow the
PKCS #1 v1.5 standard, it also provides PKCS #1 v1.5 encryption and signatures.