You can clone with
HTTPS or Subversion.
This would break BC but phpseclib's Crypt_RSA seems much more feature packed then the RSA implementation in ZF. PEAR's own Crypt_RSA has deprecated itself in favor of phpseclib's implementation.
Among other features phpseclib's Crypt_RSA supports... more key formats, key conversion, PSS signing and OAEP encryption.
This issue was ported from the ZF2 Jira Issue Tracker at
Known GitHub users mentioned in the original message or comment:
We will not add any new features or functionality for ZF1.
Please look at ZF2 there we have a new component for this. Thanks!