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  • What is Collision Free? And how does it work?
  • What is HMAC(Keyed-Hash Message Authentication Code)? And how does it work?
  • How authentication can be achieved with HMAC?

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Collision free is the desired effect of computational methods behind hashing algorithms. When a hashing algorithm is collision free it means that for each input to the hashing algorithm the resulting hash is unique and cannot be duplicated with a different input.

An HMAC is the result of a algorithm typically described as a key derivation function or technique of key stretching. NIST currently recommends the PBKDF2 algorithm to generate an HMAC.

An HMAC can be used to derive a strong irreversible hash based on a user's input, such as a password.

For details on proper implementation of an HMAC for authentication please refer to NIST SP 800-132

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