Message Integrity Check MIC
A message integrity check, or MIC, is a security technique that verifies that a message is coming from a genuine source and hasn’t been changed or tampered with during transmission. In the most secure implementations, it works as a cryptographic value often called a “fingerprint” or digest that is computed from the message data and a secret key.
How a Message Integrity Check Works
A particular sequential procedure is followed by both the sender and the recipient when confirming the integrity of a message:
- Generation: To produce the MIC, the sender uses a cryptographic method (such a hash function) in conjunction with a secret key.
- Transmission: Both the produced MIC and the original message are sent to the recipient by the sender.
- Recalculation: The recipient uses the same algorithm and secret key to carry out the precise same calculation on the message after receiving it.
- Comparison: The recipient contrasts the sender’s MIC with their own newly created one.
- Match: If the values match, the message is regarded as genuine and unaltered.
- Mismatch: The message is rejected as tampered with or fabricated if they do not match.
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Simple example
Message:
Transfer ₹10,000
Generated MIC:
A9F4C2D1...
If attacker changes amount to ₹100,000 → MIC verification fails
Key Technologies and Algorithms
MICs are different from simple hashes since they usually need a secret key to provide both integrity and authentication, even though they are really a sort of Message Authentication Code (MAC).
- Modern Algorithms: Current Secure Systems’ preferred algorithms are HMAC-SHA256, HMAC-SHA1, or AES-CMAC.
- Legacy Algorithms: MD5 and other older techniques are being viewed as legacy and insecure.
- Digital Signatures: Although they are comparable to MICs, digital signatures add the feature of non-repudiation that is, the inability of the sender to retract the message by utilizing asymmetric (public/private key) cryptography.
MIC in Wireless Security (WPA/WPA2)
Wi-Fi security is the most well-known use for MIC. As part of the previous TKIP (WPA) standard, the MIC algorithm was known as “Michael.”
A special security mechanism known as MIC Countermeasures was developed because the “Michael” method was mathematically inferior to current standards:
- Two MIC failures within 60 seconds are interpreted by a router as an active “chop-chop” assault.
- Everyone will be forced to re-authenticate using new keys when the router instantly stops all wireless communication for 60 seconds.
The integrity check is managed by the far more reliable CBC-MAC (Cipher Block Chaining Message Authentication Code) in contemporary WPA2 and WPA3 (using CCMP/AES).
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MIC vs. MAC vs. ICV
Because of their frequent interchangeability, these phrases might be confusing:
| Term | Full Name | Context |
| MIC | Message Integrity Check | General term; often used specifically in 802.11 (Wi-Fi) standards. |
| MAC | Message Authentication Code | The broader cryptographic term for a keyed hash used for integrity. |
| ICV | Integrity Check Value | Often refers to the unkeyed checksum (like CRC-32) used in old WEP security |
Importance and Applications
Man-in-the-middle attacks, bit-flip detection, and malicious modification prevention all depend on MICs. They are commonly used in many different networking layers:
- Routing Protocols: OSPF and BGP use routing protocols to guard against route injection and spoofing attacks on routing updates and sessions.
- Wireless Security: Used to guarantee frame integrity in WPA/WPA2 (802.11).
- VPNs: Use of VPNs in IPsec is necessary to guarantee authentication and packet integrity.
What MIC Does Not Provide
It is crucial to remember that a message integrity check does not offer confidentiality; as it does not encrypt the message content, the data is still accessible to third parties until an additional encryption procedure is applied. It also doesn’t offer non-repudiation unless it’s a part of a digital signature system.
Analogy: Comparatively speaking, picture mailing a sealed envelope with a distinctive wax seal on the back. The wax seal is the MIC, and the message within is the data. The recipient can tell a letter has been opened or altered if the envelope is delivered with a broken seal or one that differs from the sender’s distinctive stamp. The seal simply verifies that the contents are exactly as the sender intended; it does not prevent someone from bringing the envelope up to the light to read it.