# Hash Algorithm

Hash Algorithm definition in **Computer Security** terms:

Acronym(s): *None*

Definition(s): Algorithm that creates a hash based on a message.

**Source(s):** NIST SP 800-77

Synonym(s): Hash Function

A function on bit strings in which the length of the output is fixed. The output often serves as a condensed representation of the input.

**Source(s):** FIPS 202 A function that maps a bit string of arbitrary length to a fixed length bit string. Secure hash functions (FIPS180) satisfy the following properties: 1. One-Way. It is computationally infeasible to find any input that maps to any pre-specified output. 2. Collision Resistant. It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** FIPS 201-2 A mathematical function that maps a string of arbitrary length (up to a predetermined maximum size) to a fixed length string.

**Source(s):** FIPS 198-1 A function that maps a bit string of arbitrary length to a fixed length bit string. Approved hash functions are specified in FIPS 180 and are designed to satisfy the following properties: 1. (One-way) It is computationally infeasible to find any input that maps to any new pre-specified output, and 2. (Collision resistant) It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** FIPS 186-4 A function that maps a bit string of arbitrary length to a fixed-length bit string. The function is expected to have the following three properties:

1. Collision resistance (see Collision resistance),

2. Preimage resistance (see Preimage resistance) and

3. Second preimage resistance (see Second preimage resistance).

Approved hash functions are specified in FIPS 180-4.

**Source(s):** NIST SP 800-107 A function that maps a bit string of arbitrary length to a fixed length bit string. Approved hash functions are designed to satisfy the following properties:

1. (One-way) It is computationally infeasible to find any input that maps to any pre-specified output, and

2. (Collision resistant) It is computationally infeasible to find any two distinct inputs that map to the same output.

Approved hash functions are specified in FIPS 180-3.

**Source(s):** NIST SP 800-108 A function that maps a bit string of arbitrary length to a fixed length bit string. Approved hash functions are designed to satisfy the following properties:

1. (One-way) It is computationally infeasible to find any input that maps to any pre-specified output, and

2. (Collision resistant) It is computationally infeasible to find any two distinct inputs that map to the same output.

Approved hash functions are specified in FIPS 180-3. In some EAP methods, hash functions are used in digital signatures and to build key derivation functions and message authentication codes.

**Source(s):** NIST SP 800-120 An algorithm that computes a numerical value (called the hash value) on a data file or electronic message that is used to represent that file or message, and depends on the entire contents of the file or message. A hash function can be considered to be a fingerprint of the file or message.

**Source(s):** NIST SP 800-152 A function that maps a bit string of arbitrary length to a fixed-length bit string.

**Source(s):** NIST SP 800-56C NIST SP 800-57 Part 1 Rev. 3 A function that maps a bit string of arbitrary length to a fixed length bit string. Approved hash functions satisfy the following properties:

1. (One-way) It is computationally infeasible to find any input that maps to any pre-specified output, and

2. (Collision free) It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** NIST SP 800-57 Part 3 Rev. 1 A function that maps a bit string of arbitrary length to a fixed length bit string. Approved hash functions satisfy the following properties:

1. (One-way) It is computationally infeasible to find any input that maps to any pre-specified output, and

2. (Collision resistant) It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** NIST SP 800-63-2 A (mathematical) function that maps values from a large (possibly very large) domain into a smaller range. The function satisfies the following properties: 1. (One-way) It is computationally infeasible to find any input that maps to any pre-specified output; 2. (Collision free) It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** NIST SP 800-90A Rev. 1 A function that maps a bit string of arbitrary length to a fixed-length bit string. Approved hash functions are expected to satisfy the following properties:

1. One-way: It is computationally infeasible to find any input that maps to any pre-specified output, and

2. Collision resistant: It is computationally infeasible to find any two distinct inputs that map to the same output.

**Source(s):** NIST SP 800-56A Rev. 2 NIST SP 800-56B Rev. 1

reference: CSRC Glossary

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