Page 251 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 14: Authentication

z z Message is captured. Notes
z z Recipient's public key is retrieved.
z z One-time symmetric session key is generated.
z z Encryption operation is performed on the message using the session key.
z z Session key is encrypted using the recipient's public key.
z z Encrypted session key is included with the encrypted message.
z z Message is sent.
The following figure 14.15 shows the sequence of decrypting with the addition of the supporting
elements of public key cryptography.

Figure 14.15: Sequence of Decrypting Public Key Cryptography

Source: http://technet.microsoft.com/en-us/library/aa998077(v=exchg.65).aspx

z z Message is received.
z z Encrypted message and encrypted session key are retrieved from the message.
z z Recipient's private key is retrieved.
z z Session key is decrypted with the recipient's private key.
z z Message is decrypted with decrypted session key.
z z Unencrypted message is returned to the recipient.
The sequence shows how public key cryptography provides support for the core services of
message encryption: confidentiality and data integrity.

14.4.5 Understanding How Public Key Cryptography in Digital Signatures
and Message Encryption Work Together

Digital signatures and message encryption are complimentary services. After considering how
public key cryptography integrates with each service individually, it is helpful to consider how
these services are used together.
The following figure 14.16 shows the sequence of signing and encrypting with the addition of the
supporting elements of public key cryptography.

z z Message is captured.
z z Hash value of the message is calculated.
z z Sender's private key is retrieved.
z z Recipient's public key is retrieved.
z z Hash value is encrypted with the sender's private key.
z z Encrypted hash value is appended to the message as a digital signature.
z z One-time symmetric session key is generated.
z z Encryption operation is performed on a message using the session key.
z z Session key is encrypted using the recipient's public key.

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