What Data Type and Length Should I Use for Storing Hashed Passwords in My Database?

Data Type and Length Considerations for Hashed Password Storage

When establishing database schema for password management, deciding on the appropriate data type and length for hashed passwords is crucial. This decision hinges on the chosen hashing algorithm.

Hash Algorithm and Length

Hash functions produce fixed-length results regardless of the input's size. Hash values are often represented as hexadecimal strings, which vary in length based on the algorithm used:

• MD5: 32 hexadecimal digits
• SHA-1: 40 hexadecimal digits
• SHA-256: 64 hexadecimal digits
• SHA-512: 128 hexadecimal digits

Data Type Considerations

The appropriate data type for storing hashed passwords depends on the specific hash algorithm:

• CHAR(x): Fixed-length character string, recommended for storing hashed passwords as hexadecimal strings.
• BINARY(x): Fixed-length binary string, can be used if the hashing algorithm's output can be represented as a binary string.

Specific Recommendations

For password hashing, it's not recommended to use direct hash functions but rather key-strengthening algorithms like Bcrypt or Argon2i. These algorithms generate hashed passwords of varying lengths typically represented using CHAR(60).

Additional Considerations

While it's possible to store hashed passwords as strings of hexadecimal digits, it's not recommended because it makes unhexing them easier. Additionally, it's emphasized that using simple hash functions is inadequate for secure password storage. NIST recommends SHA-256 or higher for most applications but discourages their use for password hashing.

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