Signer

1
Figure 15.5Certificate Authority
Step 2
Signer
Certificate Authority
PUBLIC KEY
Request Certificate
Step 3
Issue
CA Certificate
This is signers public key
PRIVATE KEY
Step 1
PUBLIC KEY
Isl Certificate Authority
Sign (Private Key)
Step 4
Step 6
Verify?
Step 5
Signature
Signature


Plaintext
Plaintext
2
Step 1 Signer creates its own public key and
private key. Step 2 Signer requests
certificate from certification authority
(CA). Step 3 CA issues a certificate of
signers public key, signed by CAs private
key. Step 4 Singer uses one-way hash
function to create message digest from plaintext
(Step 1 from Figure 15.4) and
encrypts message digest with private key to
create signature (Step 2 from
Figure 15.4). Step 5 Signer sends plaintext
and signature to recipient (Step 3 form Figure
15.4). Step 6 Recipient uses one-way hash
function to create message digest from plaintext
(Step 4 from Figure 15.4),
decrypts signature with public key to create
message digest (Step 5 from Figure
15.4), and compares the two message digests (Step
6 from Diagram 15.4).