Digital Certificates

1. Digital Certificates

2. Digital certificates serve the purpose of validating the data sent to ensure that it has not been tampered with. • It uses a method called ‘hashing’ to do this. This hash is a unique string created from the data. It is then encrypted with the sender’s private key before being sent. • This hash can then be decrypted by the sender’s public key by any one else thus proving that the data received is from the sender (as the only one with access to the private key is the sender). • After this, the receiver creates a hash from the data received, and checks the two hashes against each other. If they do not match, then the data has been tampered with.

3. Encryption Steps • The message is hashed to produce a message ‘digest’ • The message digest is encrypted with Ania’s private key, this becomes the signature • The signature is appended to the message • The message is encrypted using Bob’s public key. • The encrypted message is sent to Bob

4. Decryption Steps • Bob decrypts the message with his own private key • Bob decrypts the signature with Ania’s public key to retrieve the original message digest. • The decrypted message is hashed again to reproduce the message digest. • If the decrypted digest equals the reproduced digest, the message has not been tampered with.