A Message Integrity Code (MIC) is a cryptographic checksum attached to a message to verify its integrity during transmission. By generating a MIC from the message content using a specific algorithm, the sender enables the receiver to detect any unauthorized changes or tampering. If the received MIC matches the recalculated MIC, the message is considered authentic and unaltered. MICs are commonly used in secure communications, such as wireless network authentication protocols like WPA, to prevent attackers from modifying messages without detection. Unlike digital signatures, MICs do not provide non-repudiation but focus solely on message integrity.