RNG

Synchronous random number generation inside the TEE. The randomness is derived from TEE-internal entropy combined with optional personalization data, ensuring that the output is unpredictable to all parties — including the node operator.

Proposer bias. A block proposer could theoretically simulate RNG outputs and selectively order transactions to influence outcomes. Seismic's TEE setup largely mitigates this, but high-stakes applications should consider commit-reveal schemes. See Footguns — RNG Proposer Bias for details.

Input

Raw bytes in the following layout:

Offset	Field	Type	Description
[0:4]	output length	4 bytes (uint32)	Number of random bytes to generate
[4:]	personalization	arbitrary bytes	Optional data to influence the RNG output

Output

Bytes	Type	Description
random bytes	bytes	Random bytes of the requested length

Built-in helpers

Seismic Solidity provides built-in functions that call this precompile and automatically cast the result to the appropriate shielded type. If you use these, you don't need to deal with the raw precompile interface or manual casting.

Shielded integers:

• unsafe_rng_u8() → suint8

• unsafe_rng_u16() → suint16

• unsafe_rng_u32() → suint32

• unsafe_rng_u64() → suint64

• unsafe_rng_u96() → suint96

• unsafe_rng_u128() → suint128

• unsafe_rng_u256() → suint256

Shielded fixed bytes:

• unsafe_rng_b1() → sbytes1

• ...

• unsafe_rng_b32() → sbytes32

Use cases

• Shuffling hidden card decks or secret orderings

• Generating nonces for on-chain cryptographic operations

Examples

Without personalization

suint256 random = unsafe_rng_u256();

With personalization

To pass personalization bytes, call the precompile directly at 0x64:

function getRandomBytesWithPersonalization(
    uint32 numBytes,
    bytes memory pers
) internal view returns (bytes memory) {
    // Without personalization, use abi.encodePacked(numBytes) instead
    (bool success, bytes memory result) = address(0x64).staticcall(
        abi.encodePacked(numBytes, pers)
    );
    require(success, "RNG precompile failed");
    return result;
}