Precompiles

Seismic adds six precompiled contracts to the EVM, giving smart contracts access to cryptographic primitives that would be prohibitively expensive to implement in Solidity. All standard Ethereum precompiles (e.g. ecrecover, sha256) remain available at their usual addresses.

Precompiles are called like regular contracts using staticcall or call to their fixed addresses. They execute native code rather than EVM bytecode, making them significantly cheaper and faster than equivalent Solidity implementations.

All precompiles expect raw concatenated bytes as input, not ABI-encoded data. Use abi.encodePacked (not abi.encode) when constructing input in Solidity.

These are the precompiles Seismic adds:

Name	Address	Purpose
RNG	0x64	Securely generate random bytes inside the TEE
ECDH	0x65	Derive an AES key from a private key and a public key
AES-GCM Encrypt	0x66	Encrypt data with AES-256-GCM authenticated encryption
AES-GCM Decrypt	0x67	Decrypt data with AES-256-GCM authenticated encryption
HKDF	0x68	Derive a 32-byte key from input key material
secp256k1 Sign	0x69	Sign a message hash with a secp256k1 private key

Common pattern: Encrypted events

A frequent use of the precompiles is encrypting event data so that only the intended recipient can read it. The typical flow chains ECDH and AES-GCM Encrypt together:

// 1. Derive an AES key via ECDH
sbytes32 aesKey = sbytes32(ecdh(contractPrivKey, recipientCompressedPubKey));

// 2. Generate a random nonce
uint96 nonce = uint96(unsafe_rng_u96());

// 3. Encrypt the sensitive data
bytes memory encrypted = aes_gcm_encrypt(aesKey, nonce, plaintext);

// 4. Emit a regular event with the encrypted bytes
emit EncryptedData(msg.sender, recipient, nonce, encrypted);

For a complete walkthrough of this pattern, see Events.