IBM WebSphere V5.0 Security - CGISecurity

Public key cryptography involves the use of different keys for encrypting and
decrypting functions. If you encrypt something with key 1, you can only decrypt it
with key 2, as shown in Figure 2-4.
Key 1 Key 2
Plaintext Encryption Ciphertext Decryption Plaintext
Figure 2-4 Public key concept
This architecture allows the use of one of the keys as a private key. This means
that nobody can have access to this key except the owner. The other key can be
used as a public key. If a user wants to send an encrypted message to another
person, he or she will get the other person‘s public certificate, encrypt the
message and send it. The message can be decrypted only by the owner of the
private key.
1
2
3
Alice
Plain text
B
public
Encrypted text
B
private
Plain text
Bob
Alice
Plain text
A
private
Encrypted text
A
public
Plain text
Bob
Figure 2-5 Using private key cryptography
Figure 2-5 shows a sample communication between two persons: Alice and Bob.
1. Alice wants to communicate with Bob but she does not want anybody to read
the messages. She will use Bob‘s public key to encrypt the message.
2. Alice sends the message to Bob.
3. Bob uses his private key to decrypt the message.
Chapter 2. Security fundamentals 13