CBC-MAC

CBC-MAC

CBC-MAC, short for Cipher Block Chaining Message Authentication Code, is a widely used cryptographic technique that provides message integrity and authenticity. It is a type of message authentication code (MAC) that is based on the Cipher Block Chaining (CBC) mode of operation.

Overview

CBC-MAC is commonly used in various cryptographic protocols and applications to ensure the integrity and authenticity of transmitted data. It is particularly useful in scenarios where data needs to be protected against unauthorized modifications or tampering.

The CBC-MAC algorithm operates by dividing the input message into fixed-size blocks and processing them one at a time. Each block is XORed with the previous ciphertext block before being encrypted using a symmetric encryption algorithm, such as AES (Advanced Encryption Standard). The final ciphertext block is then used as the MAC value for the entire message.

Security Properties

CBC-MAC provides several important security properties that make it suitable for secure communication:

1. **Message Integrity**: CBC-MAC ensures that the received message has not been modified during transmission. Any alteration in the message will result in a different MAC value, indicating tampering.

2. **Message Authenticity**: The MAC value generated by CBC-MAC can be used to verify the authenticity of the message. Only the sender, who possesses the secret key, can generate the correct MAC value.

3. **Unforgeability**: CBC-MAC is resistant to forgery attacks, meaning that it is computationally infeasible for an attacker to generate a valid MAC value for a message without knowing the secret key.

Usage and Applications

CBC-MAC is widely used in various cryptographic protocols and applications, including:

1. **Secure Communication**: CBC-MAC can be used to ensure the integrity and authenticity of transmitted data in secure communication channels, such as VPNs (Virtual Private Networks) and SSL/TLS (Secure Sockets Layer/Transport Layer Security) protocols.

2. **Data Storage**: CBC-MAC can be employed to protect the integrity of stored data, such as in file systems or databases. By calculating the MAC value of the data and storing it alongside the data, any unauthorized modifications can be detected.

3. **Digital Signatures**: CBC-MAC can be used as a building block for constructing digital signature schemes. By combining CBC-MAC with a public-key encryption algorithm, a secure and efficient digital signature scheme can be achieved.

See Also

• Cipher Block Chaining (CBC)
• Message Authentication Code (MAC)
• Advanced Encryption Standard (AES)