Review the paragraph from The Code Book. Ordinarily, if Alice wants to use RSA to encrypt a message to Bob, she looks up his public key and then applies RSA's one-way function to the message. Conversely, Bob decrypts the ciphertext by using his private key to reverse RSA's one-way function. Both processes require considerable mathematical manipulation, so encryption and decryption can, if the message is long, take several minutes on a personal computer.

Which transitional word has the same meaning as "on the other hand”?

ordinarily
conversely
manipulation
encryption