Marinade Limited - leading the way in paperless business practice
Flag M
Flag A
Flag R
Flag I
Flag N
2nd subst
Flag D
Flag E

Digital signatures 1: Authenticity

  A cryptic message
  A clear message
Bob and the message

Above you see a picture of Bob. He has just received the encrypted message you can see in the form above, and he is wondering where it came from. You will be able to help him, because authenticity can be proven with the aid of cryptography. This is how:

Bob knows that the message can come from one of three senders: Alice, Amy or Anna. The cryptographic keys they use for communication with Bob are shown above. If you enter a key in the box below, and press the "Decrypt" button, Bob's crypto system will deliver the decrypted version of the message to him. By experimenting with different keys, you should be able to determine who sent the message. Press the correct button and you will progress to the next stage of the demo...

Enter a five-letter key here:

I think the message was sent by

Quick glossary:

Marinade Limited - c/o Allagraf Limited - 3 More London Riverside - London SE1 2RE
Tel +44 20 3283 4277