# Services from crypto-math.x402tookit.com on Zero

> crypto-math.x402tookit.com serves 10 paid API services for AI agents, indexed by Zero. Each is callable per call with payment handled by Zero.

Canonical page: https://www.zero.xyz/host/crypto-math.x402tookit.com
Live health (JSON, refreshed every minute): https://www.zero.xyz/host/crypto-math.x402tookit.com/health.json

## Services

- [Crypto Math Check Digits](https://www.zero.xyz/c/crypto-math-check-digits-4ae85252/llms.txt): $0.02/call via x402. Generate or validate Luhn and ISO 7064 mod 97-10 (IBAN-style) check digits for a given numeric or alphanumeric string.
- [Crypto Math: GCD, LCM & Extended Euclidean (Bézout Coefficients)](https://www.zero.xyz/c/crypto-math-gcd-lcm-extended-euclidean-b-zout-coefficients-56a1f248/llms.txt): $0.02/call via x402. Computes GCD, LCM, and extended Euclidean Bézout coefficients for two integers, with optional batch GCD/LCM over up to 20 additional numbers.
- [Crypto Math: Chinese Remainder Theorem Solver](https://www.zero.xyz/c/crypto-math-chinese-remainder-theorem-solver-a99fdc21/llms.txt): $0.02/call via x402. Solves systems of simultaneous congruences (x ≡ a1 mod m1, x ≡ a2 mod m2, …) using the Chinese Remainder Theorem, supporting both coprime and non-coprime moduli.
- [Crypto Math: Modular Exponentiation (mod-pow)](https://www.zero.xyz/c/crypto-math-modular-exponentiation-mod-pow-bd28b208/llms.txt): $0.02/call via x402. Computes base^exp mod m for big integers (up to 4096 bits), accepting decimal or 0x hex inputs, returning both decimal and hex results.
- [Crypto Math Encoding Converter](https://www.zero.xyz/c/crypto-math-encoding-converter-4be81785/llms.txt): $0.02/call via x402. Convert public byte strings between hex, base64, and base64url (RFC 4648) with strict decoding and optional expected-length verification.
- [Crypto Math Primality Test](https://www.zero.xyz/c/crypto-math-primality-test-7b337b1c/llms.txt): $0.02/call via x402. Runs a deterministic Miller-Rabin primality test on a big integer (up to 1024 bits), plus optionally returns the nearest previous and next primes.
- [Crypto Math Entropy Calculator](https://www.zero.xyz/c/crypto-math-entropy-calculator-041f6f8e/llms.txt): $0.02/call via x402. Computes Shannon entropy, min-entropy, collision entropy, and efficiency in bits per symbol from a frequency table of counts or probabilities.
- [Crypto Math: Modular Multiplicative Inverse](https://www.zero.xyz/c/crypto-math-modular-multiplicative-inverse-87efc29e/llms.txt): $0.02/call via x402. Computes the modular multiplicative inverse of a mod m, or returns the GCD proving no inverse exists when gcd(a,m) > 1.
- [Crypto Math – Elliptic Curve Parameters & On-Curve Point Validation](https://www.zero.xyz/c/crypto-math-elliptic-curve-parameters-on-curve-point-validation-16145e9f/llms.txt): $0.02/call via x402. Returns the SEC 2 public domain parameters (p, n, G, a, b) for secp256k1, P-256, or P-384, and optionally validates whether a given public point lies on the specified curve.
- [Crypto Math RSA Arithmetic](https://www.zero.xyz/c/crypto-math-rsa-arithmetic-fdadbf3a/llms.txt): $0.02/call via x402. Analyzes RSA public key parameters (modulus bits, exponent validity, NIST strength) or demonstrates a toy RSA encryption/decryption round-trip using tiny primes.

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

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