David Bombal

#535: Encryption vs Hashing: What's the real difference?

Feb 2, 2026
Guest
Mike Pound
Dr. Mike Pound, computer scientist and Computerphile contributor who specializes in cryptography, explains why hashing is one-way while encryption is reversible. He covers hash properties like the avalanche effect and collisions. He also discusses rainbow tables, salting, SHA-2 vs SHA-3, length-extension attacks, and how hashing fits into signatures and integrity checks.
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INSIGHT

Hashing vs Encryption: Different Tools

  • Hashing and encryption belong to cryptography but serve different purposes and properties.
  • Encryption is reversible with a key, while hashing irreversibly summarizes data into a fixed-length value.
INSIGHT

Why Hashes Look Random But Are Deterministic

  • A hash is a deterministic, fixed-length, pseudo-random summary: same input always yields the same output.
  • Hash outputs look random and reveal nothing about the original content while enabling integrity checks.
ADVICE

Never Store Plaintext Passwords

  • Don't store plaintext passwords; store hashes and compare incoming password hashes at login.
  • Hashing lets you verify a user without ever holding their original password in your database.
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