IBM WebSphere V5.0 Security - CGISecurity

Public key cryptography involves the use of different keys for encrypting anddecrypting functions. If you encrypt something with key 1, you can only decrypt itwith key 2, as shown in Figure 2-4.Key 1 Key 2Plaintext Encryption Ciphertext Decryption PlaintextFigure 2-4 Public key conceptThis architecture allows the use of one of the keys as a private key. This meansthat nobody can have access to this key except the owner. The other key can beused as a public key. If a user wants to send an encrypted message to anotherperson, he or she will get the other person‘s public certificate, encrypt themessage and send it. The message can be decrypted only by the owner of theprivate key.123AlicePlain textBpublicEncrypted textBprivatePlain textBobAlicePlain textAprivateEncrypted textApublicPlain textBobFigure 2-5 Using private key cryptographyFigure 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 readthe 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