AES Key Strength Analyzer

Summary

AES Key Strength Analyzer decodes hex or base64 key material and evaluates it against three criteria: correct bit length (128, 192, or 256 bits), sample Shannon entropy normalized for the short key length, and absence of degenerate patterns such as all-zero keys, all-same-byte keys, or sequential byte runs. These checks can detect obvious mistakes but cannot prove that a key came from a cryptographically secure random generator.

How it works

1. Paste your AES key as a hex string (e.g. a1b2c3d4...) or base64 string into the input field.
2. The tool auto-detects the encoding format and decodes the raw bytes.
3. Key length is checked: valid AES sizes are 128-bit (16 bytes), 192-bit (24 bytes), or 256-bit (32 bytes).
4. Sample Shannon entropy is normalized against log₂(key bytes), the maximum observable value in a 16–32 byte sample.
5. Weakness patterns are tested: all-zero bytes, all-same-byte, sequential ramps, and low unique byte count.
6. A combined strength score and pass/fail report is displayed with actionable recommendations.

Use cases

• Validate AES keys generated by your application before deploying to production.
• Audit legacy configuration files for weak or placeholder encryption keys.
• Verify that a key derivation function (KDF) is producing high-entropy output.
• Check manually typed keys for accidental patterns or truncation errors.
• Teach developers how key entropy and bit length affect AES security.
• Quickly confirm a 256-bit key is exactly 32 bytes (64 hex characters).

Frequently Asked Questions