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Symmetric Message Authentication Codes

Symmetric Message Authentication Codes. Prof. Ravi Sandhu. MESSAGE AUTHENTICATION CODES. INSECURE CHANNEL. Plaintext + MAC. Yes/No. Plain- text. MAC Algorithm M. Verification Algorithm V. A. B. K. K. MAC = MD of plaintext + K. CURRENT GENERATION MAC ALGORITHMS.

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Symmetric Message Authentication Codes

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  1. Symmetric Message Authentication Codes Prof. Ravi Sandhu

  2. MESSAGE AUTHENTICATION CODES INSECURE CHANNEL Plaintext + MAC Yes/No Plain- text MAC Algorithm M Verification Algorithm V A B K K MAC = MD of plaintext + K

  3. CURRENT GENERATION MAC ALGORITHMS • HMAC-MD5, HMAC-SHA • IETF standard • general technique for constructing a MAC from a message digest algorithm • Older MACs are based on secret key encryption algorithms (notably DES) and are still in use • DES based MACs are 64 bit and not considered strong anymore

  4. HMAC • HMAC computation • HMACK(M) = h(Kopad || h(Kipad || M) ) • h is any message digest function • M message • K secret key • opad, ipad: fixed outer and inner padding • HMAC-MD5, HMAC-SHA

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