The 'jsrsasign' (RSA-Sign JavaScript Library) is an opensource free pure JavaScript cryptographic library supports RSA/RSAPSS/ECDSA/DSA signing/validation, ASN.1, PKCS#1/5/8 private/public key, X.509 certificate and CRL
Public page is http://kjur.github.com/jsrsasign .
Your bugfix and pull request contribution are always welcomed :)