This form is used by Bob to either (1) send Alice an encrypted message (encrypted with Alice's public key), or (2) to receive a digitally signed message from Alice.
The following is for Alice's public key:
The following is to send Bob an encrypted message. Put in the plaintext, encrypt it with Bob's public key, and send the encrypted text (ciphertext) to Bob. Only Bob will be able to read it.
The following is to check the digital signature on a message digest that purports to be from Bob. Put in the signed message digest, and decrypt it with Bob's public key. If it matches the message digest for the message, then the digest was encrypted with Bob's private key.
© 2011 Scott D. Anderson, adapted from 2005 Herbert Hanewinkel, adapted from John Hanna's RSA implementation