AIMer (KPQC)

MPC-in-the-Head Digital Signature Scheme

Overview

AIMer is a digital signature algorithm developed as part of the Korean Post-Quantum Cryptography (KPQC) competition. It uses the MPC-in-the-head (MPCitH) paradigm: the signer simulates a multi-party computation protocol “in their head” and then uses a Fiat-Shamir transform to convert the resulting zero-knowledge proof into a non-interactive signature.

AIMer’s security does not rely on lattice assumptions, making it a diversification choice alongside lattice-based schemes like ML-DSA, Falcon, and HAETAE. Instead, its security is based on the one-wayness of the AIM permutation and the soundness of the underlying MPC protocol.

How it works:

The secret key defines a witness for a one-way function (the AIM permutation).
To sign, the signer simulates an MPC protocol that verifies knowledge of the witness, producing a transcript.
The Fiat-Shamir heuristic converts this interactive proof into a non-interactive signature by replacing the verifier’s challenges with hash function outputs.
The verifier checks the consistency of the MPC transcript against the public key.

Specifications

Parameter Set	KPQC Level	Description
AIMer-128f	1	Targeting 128-bit post-quantum security, fast variant
AIMer-192f	3	Targeting 192-bit post-quantum security, fast variant
AIMer-256f	5	Targeting 256-bit post-quantum security, fast variant

Core operations:

KeyGen() — Generate a signing key pair (secret witness + public image under AIM)
Sign(sk, msg) — Produce a signature by simulating the MPC protocol and applying Fiat-Shamir
Verify(pk, msg, sig) — Verify the MPC transcript consistency against the public key

The “f” suffix indicates the fast variant, optimized for signing speed at the cost of somewhat larger signatures.

Security

Security notion: EUF-CMA (existential unforgeability under chosen-message attack)
Hardness assumption: One-wayness of the AIM permutation
Proof system: MPC-in-the-head (MPCitH) — the signer simulates an MPC protocol proving knowledge of the secret key
No lattice assumptions: Security does not depend on Module-LWE, NTRU, or any structured lattice problem
Diversification value: Provides a hedge against potential future breakthroughs in lattice cryptanalysis, since it relies on fundamentally different mathematical assumptions
Korean standardization: Developed and evaluated under the KPQC competition framework

Hardware Acceleration

AIMer’s computational cost is dominated by field arithmetic and hash function evaluations within the MPC simulation. Standard SIMD acceleration for hash functions (SHA-3 / SHAKE) applies.

Acceleration	Target	Description
AVX-2	x86-64	Parallel field arithmetic and hash evaluations
NEON	ARM	Parallel field arithmetic and hash evaluations

Platform Support

AIMer is implemented across the MetaMUI platform suite:

Platform	Language	Implementation Path
Native	C	`metamui-crypto-c/`
Systems	Rust	`metamui-crypto-rust/`
Backend	Go	`metamui-crypto-go/`
Data Science	Python	`metamui-crypto-python/`
JVM	Java	`metamui-crypto-java/`
JVM/Android	Kotlin	`metamui-crypto-kotlin/`
.NET	C#	`metamui-crypto-csharp/`
Apple	Swift	`metamui-crypto-swift/`
Web	TypeScript	`metamui-crypto-typescript/`
Browser/Edge	WASM	`metamui-crypto-wasm/`

API Example

// Key generation
let (pk, sk) = aimer_192f::keygen(&mut rng);

// Signing
let message = b"Document to be signed";
let signature = aimer_192f::sign(&sk, message);

// Verification
let is_valid = aimer_192f::verify(&pk, message, &signature);
assert!(is_valid);

Test Vectors

Format: KPQC KAT (Known Answer Test) vectors
Coverage: KeyGen, Sign, Verify for all parameter sets

References

KPQC Competition — Korean Post-Quantum Cryptography competition. Organized by the Korean government to standardize quantum-resistant algorithms for Korean national standards.
AIMer Specification — AIMer Algorithm Specifications and Supporting Documentation. Submitted to the KPQC competition.
MPC-in-the-Head — Ishai, Y., Kushilevitz, E., Ostrovsky, R., Sahai, A. Zero-Knowledge from Secure Multiparty Computation. STOC 2007.