Skip to main content
@tevm/voltaire
@tevm/voltaire / crypto/ModExp

​
crypto/ModExp

​
Variables

​
ModExp

const ModExp: (base, exp, modulus) => bigint & object
Defined in: src/crypto/ModExp/ModExp.js:35 ModExp - Modular Exponentiation Computes base^exp mod modulus for arbitrary-precision integers. Used by MODEXP precompile (0x05) per EIP-198/EIP-2565.

​
Type Declaration

calculateGas()
calculateGas: (baseLen, expLen, modLen, expHead) => bigint
Calculate gas cost for MODEXP operation per EIP-2565 Gas formula: max(200, floor(mult_complexity * iteration_count / 3))
Parameters
baseLen
bigint Length of base in bytes
expLen
bigint Length of exponent in bytes
modLen
bigint Length of modulus in bytes
expHead
bigint First 32 bytes of exponent as BigInt (for leading zeros calc)
Returns
bigint Gas cost
See
https://eips.ethereum.org/EIPS/eip-2565
Since
0.0.0
Example
import { ModExp } from './crypto/ModExp/index.js';

// Calculate gas for 2^3 mod 5
const gas = ModExp.calculateGas(1n, 1n, 1n, 3n);
console.log(gas); // 200n (minimum)
modexp()
modexp: (base, exp, modulus) => bigint
Modular exponentiation: base^exp mod modulus Computes arbitrary-precision modular exponentiation using native BigInt. Used by MODEXP precompile (0x05) per EIP-198. WARNING: This implementation is for general use. For cryptographic applications, consider timing attack resistance.
Parameters
base
bigint Base value
exp
bigint Exponent value
modulus
bigint Modulus value (must be > 0)
Returns
bigint Result of base^exp mod modulus
See
https://eips.ethereum.org/EIPS/eip-198
Since
0.0.0
Throws
If modulus is zero
Example
import { ModExp } from './crypto/ModExp/index.js';

// Compute 2^10 mod 1000 = 24
const result = ModExp.modexp(2n, 10n, 1000n);
console.log(result); // 24n

// RSA verification: signature^e mod n
const verified = ModExp.modexp(signature, e, n);
modexpBytes()
modexpBytes: (baseBytes, expBytes, modBytes) => Uint8Array<ArrayBufferLike>
Modular exponentiation with byte array inputs/outputs Computes base^exp mod modulus where inputs are big-endian byte arrays. Output is padded to modulus length per EIP-198 spec.
Parameters
baseBytes
Uint8Array<ArrayBufferLike> Base as big-endian bytes
expBytes
Uint8Array<ArrayBufferLike> Exponent as big-endian bytes
modBytes
Uint8Array<ArrayBufferLike> Modulus as big-endian bytes
Returns
Uint8Array<ArrayBufferLike> Result as big-endian bytes, padded to modulus length
See
https://eips.ethereum.org/EIPS/eip-198
Since
0.0.0
Throws
If modulus is zero
Example
import { ModExp } from './crypto/ModExp/index.js';

const base = new Uint8Array([0x02]); // 2
const exp = new Uint8Array([0x03]);  // 3
const mod = new Uint8Array([0x05]);  // 5

const result = ModExp.modexpBytes(base, exp, mod);
console.log(result); // Uint8Array([0x03]) = 3

​
See

​
Since

0.0.0

​
Example

import { ModExp } from './crypto/ModExp/index.js';

// Using BigInt directly
const result = ModExp.modexp(2n, 10n, 1000n); // 24n

// Using byte arrays (EIP-198 format)
const base = new Uint8Array([0x02]);
const exp = new Uint8Array([0x0a]);
const mod = new Uint8Array([0x03, 0xe8]);
const resultBytes = ModExp.modexpBytes(base, exp, mod);

// Calculate gas cost
const gas = ModExp.calculateGas(1n, 1n, 2n, 10n);

​
Functions

​
calculateGas()

calculateGas(baseLen, expLen, modLen, expHead): bigint
Defined in: src/crypto/ModExp/calculateGas.js:22 Calculate gas cost for MODEXP operation per EIP-2565 Gas formula: max(200, floor(mult_complexity * iteration_count / 3))

​
Parameters

baseLen
bigint Length of base in bytes
expLen
bigint Length of exponent in bytes
modLen
bigint Length of modulus in bytes
expHead
bigint First 32 bytes of exponent as BigInt (for leading zeros calc)

​
Returns

bigint Gas cost

​
See

https://eips.ethereum.org/EIPS/eip-2565

​
Since

0.0.0

​
Example

import { ModExp } from './crypto/ModExp/index.js';

// Calculate gas for 2^3 mod 5
const gas = ModExp.calculateGas(1n, 1n, 1n, 3n);
console.log(gas); // 200n (minimum)

​
modexp()

modexp(base, exp, modulus): bigint
Defined in: src/crypto/ModExp/compute.js:29 Modular exponentiation: base^exp mod modulus Computes arbitrary-precision modular exponentiation using native BigInt. Used by MODEXP precompile (0x05) per EIP-198. WARNING: This implementation is for general use. For cryptographic applications, consider timing attack resistance.

​
Parameters

base
bigint Base value
exp
bigint Exponent value
modulus
bigint Modulus value (must be > 0)

​
Returns

bigint Result of base^exp mod modulus

​
See

https://eips.ethereum.org/EIPS/eip-198

​
Since

0.0.0

​
Throws

If modulus is zero

​
Example

import { ModExp } from './crypto/ModExp/index.js';

// Compute 2^10 mod 1000 = 24
const result = ModExp.modexp(2n, 10n, 1000n);
console.log(result); // 24n

// RSA verification: signature^e mod n
const verified = ModExp.modexp(signature, e, n);

​
modexpBytes()

modexpBytes(baseBytes, expBytes, modBytes): Uint8Array<ArrayBufferLike>
Defined in: src/crypto/ModExp/modexpBytes.js:28 Modular exponentiation with byte array inputs/outputs Computes base^exp mod modulus where inputs are big-endian byte arrays. Output is padded to modulus length per EIP-198 spec.

​
Parameters

baseBytes
Uint8Array<ArrayBufferLike> Base as big-endian bytes
expBytes
Uint8Array<ArrayBufferLike> Exponent as big-endian bytes
modBytes
Uint8Array<ArrayBufferLike> Modulus as big-endian bytes

​
Returns

Uint8Array<ArrayBufferLike> Result as big-endian bytes, padded to modulus length

​
See

https://eips.ethereum.org/EIPS/eip-198

​
Since

0.0.0

​
Throws

If modulus is zero

​
Example

import { ModExp } from './crypto/ModExp/index.js';

const base = new Uint8Array([0x02]); // 2
const exp = new Uint8Array([0x03]);  // 3
const mod = new Uint8Array([0x05]);  // 5

const result = ModExp.modexpBytes(base, exp, mod);
console.log(result); // Uint8Array([0x03]) = 3