I'm developing a SOAP application where java clients provide authentication 
information with each call, and the server verifies the auth info before dispatching 
calls.

- The length of this auth info will typically be 50 bytes.
- Approximately half (the leading half) of these auth info bytes will be different 
with each call.

I want to encrypt this auth info each time the client makes a soap call, I was 
thinking of using RSA: the client encrypting the info using the public key and the 
server decrypting using the private key.

Q. I understand that RSA (asymmetric) is slower than symmteric but would this still be 
the case given the size of the plaintext
Q. Is using RSA to encrypt small packets in-secure?, if so should I artificially 
increase the size of the plaintext by introducing random noise?
Q. If I instead use a block cipher (say AES) should I use a different IV for every 
encryption, if so the client would have to send the IV (and the length of the IV) 
along with the ciphertext?
Q. Would Base64 or Hex be the best encoding option to use to transmit the cipher text 
via soap (HTTP/XML) to the server?

comments appreciated.
phil

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