Hi everyone, I only have problems with the second half of this question....

Alice has RSA public key KA = (10823, 5). Bob has RSA private key LB = (10757, 131).

They have agreed that Alice will sign her messages digitally. As plaintext signature
she will use the ciphertext obtained using Bob's public key.
One day, Bob receives the message (4029, 6636); he thinks it is from Alice. The fi rst number is a ciphertext unit, the second number is the corresponding ciphertext

Decrypt the ciphertext unit. Determine whether the signature is valid.

So im pretty sure I have been able to decrypt the ciphertext unit (i obtained the answer 5114 for that) but I get a little confused with the signature part. I think it might be something to do with using Alice's public key but im not quite sure. Obviously the maths is fairly easy once the theory is know, but i dont quite know it!

Any ideas?