First, many thanks for all your valuable reply. It seems Crypt::OpenSSL::RSA and Crypt::PK::RSA can do the job as Crypt::RSA does. It seems Crypt::PK::RSA is pretty new and I cannot find any detailed documentation on it. Anyway I benchmarked Crypt::RSA and Crypt::OpenSSL::RSA with a group of 20 digit strings and find out that the speed to encrypt/decrypt using OpenSSL is about 10 times faster than Crypt::RSA, which surprised me a bit. After some more testing, we might use Crypt::OpenSSL::RSA to replace Crypt::RSA.