Cryptographic Hash Functions: MD5, SHA-1, SHA-256, and HMAC Guide
Explore the mathematical foundations of one-way hash digests, the avalanche effect, and why modern systems rely on SHA-256 and HMAC.
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What is a Cryptographic Hash Function?
A cryptographic hash function is a one-way mathematical algorithm that converts an arbitrary block of data into a fixed-length string of characters (its digital fingerprint).
Fundamental Properties
- One-Way: It is computationally infeasible to reverse a hash back to its original input.
- Avalanche Effect: Changing a single bit in the input causes a completely different hash output.
- Collision Resistance: Finding two distinct inputs that produce identical hash outputs must be virtually impossible.
MD5 and SHA-1 are Deprecated: Known collision vulnerabilities mean MD5 and SHA-1 should never be used for password hashing or digital signatures; use at least SHA-256.
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β Frequently Asked Questions (FAQ)
What is HMAC? βΎ
HMAC (Hash-based Message Authentication Code) calculates a hash using a secret key to verify both data integrity and message authenticity.