🔒Cryptographic Hash Function

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Also known as: Crypto Hash, Secure Hash Function

A function mapping input data to a fixed-length digest, designed to be collision-resistant and irreversible.

DESCRIPTION

A cryptographic hash function transforms data of arbitrary size into a fixed-length digest with strong security properties: preimage resistance, second preimage resistance, and collision resistance. Hashes underpin integrity checks, digital signatures, password storage, and blockchain. Modern standards include SHA-2 and SHA-3. Weak or broken hashes like MD5 and SHA-1 should be avoided for security-sensitive uses.

ALTERNATIVE DEFINITIONS

NIST

Function that maps a bit string of arbitrary length to a fixed-length bit string; designed to have the properties of preimage resistance, second preimage resistance and collision resistance.

Lists the three core security properties explicitly.

Source

OWASP

A cryptographic hash function is a deterministic function that maps data of arbitrary size to a fixed-size value and is designed to be a one-way function.

Emphasizes determinism and one-way property for security.

Source

IETF RFC 4949

cryptographic hash function: A hash function whose output is dependent on all its input bits and that is designed to resist cryptanalysis.

Highlights resistance to cryptanalysis and input dependency.

Source

RELATED TERMS

SHA-256 SHA-3 MD5 HMAC Digital Signature Password Hashing MAC Blockchain

COMPETING TERMS

Non-cryptographic hash function Checksum

RELATIONS

• Broader: Hash Function
• Narrower: BLAKE BLAKE2 Hash Function BLAKE3

KNOWLEDGE AREAS

Data Security Software Engineering Data Integration & Interoperability

TARGET AUDIENCE

Cybersecurity Engineer Security Architect Software Developer Data Engineer Chief Information Security Officer DevOps Engineer

EXTERNAL SOURCES

• Wikipedia - Cryptographic hash function
• NIST - Secure Hash Standard (SHA)
• OWASP - Hashing guidance for passwords
• Keccak Team - SHA-3 design and docs

TOP QUESTIONS

What makes a Cryptographic Hash Function secure?

Preimage, second preimage, and collision resistance are essential. Robust design and peer-reviewed standards like SHA-2/SHA-3 are recommended.

Category: Requirements

Why is MD5 unsafe for security applications?

MD5 is vulnerable to collisions, enabling tampering and signature forgery; use SHA-256 or better alternatives.

Category: Risks

How are cryptographic hashes used in blockchain?

Hashes link blocks, ensure data integrity, and power proof-of-work, making tampering detectable and costly.

Category: Example

What is the difference between a hash and checksum?

Checksums detect accidental corruption; cryptographic hashes resist adversarial manipulation and provide stronger integrity guarantees.

Category: Misunderstanding

How does salting improve password hashing?

Salts make precomputed attacks (rainbow tables) ineffective and ensure unique hashes for identical passwords.

Category: HowTo

What are common mistakes with Cryptographic Hash Functions?

Using outdated algorithms, skipping salting/peppering, misusing hashes for encryption, or relying on homegrown designs.

Category: Mistakes

Is SHA-1 still acceptable?

No, SHA-1 has practical collision attacks; migrate to SHA-2 or SHA-3.

Category: Opinion

How does HMAC relate to hash functions?

HMAC combines a hash with a secret key for message authentication, preventing tampering and spoofing.

Category: Overview

Where to learn more about Cryptographic Hash Functions?

Study NIST standards, OWASP guidelines, and reputable cryptography textbooks or courses.

Category: Overview