AES-GCM Decrypt

Decrypt data that was encrypted with AES-256-GCM. Verifies the authentication tag before returning the plaintext. If the tag does not match (indicating tampering or wrong key), the call fails.

Input

Raw bytes in the following layout:

Offset	Field	Type	Description
[0:32]	key	32 bytes	AES-256 key (must match encryption key)
[32:44]	nonce	12 bytes	Initialization vector
[44:]	ciphertext + auth tag	bytes	Encrypted data with authentication tag

Output

Bytes	Type	Description
plaintext	bytes	Decrypted data

Use cases

• On-chain decryption of previously encrypted data

• Decrypting messages from other contracts or users

• Verifying and reading encrypted event data within a contract

Examples

Built-in helper

function aes_gcm_decrypt(sbytes32 key, uint96 nonce, bytes memory ciphertext) view returns (bytes memory);

bytes memory plaintext = aes_gcm_decrypt(aesKey, nonce, ciphertext);

Manual usage

function aesDecrypt(
    suint256 key,
    uint96 nonce,
    bytes memory ciphertext
) internal view returns (bytes memory) {
    bytes memory input = abi.encodePacked(uint256(key), nonce, ciphertext);
    (bool success, bytes memory result) = address(0x67).staticcall(input);
    require(success, "AES-GCM Decrypt precompile failed");
    return result;
}