1. The Fundamental Distinction
• Hashing is ONE-WAY: It transforms data into a fixed-size digest that can never be reversed back into the original input. It is used for integrity verification, digital signatures, and password authentication.
• Encryption is TWO-WAY: It transforms plaintext into ciphertext so that authorized parties holding the matching secret or private key can decrypt it back into plaintext. It is used for data confidentiality in transit and at rest.
2. Comparison Summary Table
• Reversible: Hashing is No; Encryption is Yes (with key).
• Keys Required: Hashing uses No keys (plain hash); Encryption requires Symmetric (AES) or Asymmetric (RSA) keys.
• Output Length: Hashing produces fixed length (e.g. 256 bits); Encryption produces variable length proportional to plaintext.
• Primary Goal: Hashing verifies Integrity; Encryption guarantees Confidentiality.
3. Password Storage Best Practice
Passwords should NEVER be encrypted because if the encryption key is compromised, every user password in the database is exposed in plaintext. Passwords must be hashed using salted, slow, memory-hard key derivation algorithms like Argon2id, bcrypt, or scrypt.
⚠️ Important Warning: Never use plain fast hashes like SHA-256 for passwords. Attackers can test billions of fast hashes per second using consumer GPUs.