Security Levels

AegisQ supports the three ML-KEM parameter sets defined in FIPS 203. The default is ML-KEM-768 (NIST category 3). Select parameters according to your protocol, threat model, and interoperability requirements; a category is not a certification of this implementation.

Security Level Comparison

Level	Enum Value	NIST Level	Public Key	Secret Key	Capsule	Package Overhead
ML-KEM-512	SecurityLevel.ML_KEM_512	1	800 B	1632 B	768 B	796 B
ML-KEM-768	SecurityLevel.ML_KEM_768	3 (default)	1184 B	2400 B	1088 B	1116 B
ML-KEM-1024	SecurityLevel.ML_KEM_1024	5	1568 B	3168 B	1568 B	1596 B

One-shot package overhead = capsule + AES nonce (12 B) + AES auth tag (16 B). The total one-shot package size is overhead + plaintext length. Streaming uses a separate header/frame format.

NIST Security Levels Explained

• Category 1 — Uses exhaustive AES-128 key search as the NIST comparison target.
• Category 3 — Uses exhaustive AES-192 key search as the comparison target. AegisQ default.
• Category 5 — Uses exhaustive AES-256 key search as the comparison target.

These are algorithm security categories, not guarantees of a data-retention period or literal bit-security equivalence for every attack. All three hybrid modes still use AES-256-GCM for the payload.

Usage

from aegisq import AegisCipher, SecurityLevel

# Default: ML-KEM-768 (NIST Level 3)
cipher = AegisCipher()

# Explicit level selection
cipher_512 = AegisCipher(level=SecurityLevel.ML_KEM_512)    # Category 1, smallest keys
cipher_768 = AegisCipher(level=SecurityLevel.ML_KEM_768)    # Category 3 (default)
cipher_1024 = AegisCipher(level=SecurityLevel.ML_KEM_1024)  # Category 5, largest keys

Core Parameters (FIPS 203)

These are the internal ML-KEM parameters for each security level:

Level	k	η₁	η₂	dᵤ	dᵥ	pk size	sk size	ct size	ss size
ML-KEM-512	2	3	2	10	4	800 B	1632 B	768 B	32 B
ML-KEM-768	3	2	2	10	4	1184 B	2400 B	1088 B	32 B
ML-KEM-1024	4	2	2	11	5	1568 B	3168 B	1568 B	32 B

Where:

• k — Module dimension (number of polynomial vectors)
• η₁, η₂ — CBD sampling parameters for error terms
• dᵤ, dᵥ — Compression bit-widths
• pk — Public key, sk — Secret key, ct — Ciphertext (capsule), ss — Shared secret