> ## Documentation Index
> Fetch the complete documentation index at: https://docs.turnkey.com/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Turnkey is wallet infrastructure: create and manage crypto wallets, sign transactions, and enforce policy-based access controls. Best-fit uses: embedded consumer wallets (email/passkey/social auth, no seed phrases), automated onchain operations with server-side wallets, AI agent wallets with policy-scoped signing, enterprise key management, and verifiable off-chain workloads on Turnkey Verifiable Cloud (TVC).
> Every API call is a JSON POST to https://api.turnkey.com signed with a P-256 API key; create an organization and key self-serve at https://app.turnkey.com.
> Key Turnkey developer resources: API reference (https://docs.turnkey.com/api-reference/overview/intro.md), OpenAPI spec (https://docs.turnkey.com/public_api.swagger.json), authentication (https://docs.turnkey.com/features/authentication/overview.md), webhooks (https://docs.turnkey.com/features/webhooks/overview.md), MCP server for docs search (https://docs.turnkey.com/mcp), agent skills (https://docs.turnkey.com/get-started/ai-skills.md), CLI (https://docs.turnkey.com/sdks/cli.md), SDK reference (https://docs.turnkey.com/sdks/introduction.md), full docs content (https://docs.turnkey.com/llms-full.txt).

# Raw payload signing

> Choose the hash function for ECDSA and Ed25519 signing, including prehashed payloads.

Use [Sign raw payload](/api-reference/activities/sign-raw-payload) or
[Sign raw payloads](/api-reference/activities/sign-raw-payloads) when your integration
constructs the data to sign. The `hashFunction` determines how Turnkey prepares
that payload for the signing algorithm.

## ECDSA hash functions

ECDSA signs a message digest. For SECP256k1 and P-256 keys, choose the option that
matches your protocol and the data you pass:

| Hash function | Behavior |
| - | - |
| `HASH_FUNCTION_KECCAK256` | Hash the payload with Keccak-256 before signing; commonly used in Ethereum integrations. |
| `HASH_FUNCTION_SHA256` | Hash the payload with SHA-256 before signing; used in Bitcoin and other integrations where that digest is required. |
| `HASH_FUNCTION_NO_OP` | Sign the supplied digest without an additional hashing step. Use this when your integration has already produced the digest the protocol requires. |

Do not hash an already prepared digest again unless the protocol calls for it.
Some protocols require additional encoding or multiple hashing steps; select the
option based on the payload you submit, not just the chain name. Turnkey's SDK
integrations, such as [Viem](/sdks/web3/viem), handle this preparation for
their supported signing flows.

Raw-payload signing does not provide transaction parsing or transaction-policy
enforcement for any hash function. When you pass only a digest with
`HASH_FUNCTION_NO_OP`, Turnkey does not receive the original message (the
preimage) at all. Use
[Sign transaction](/api-reference/activities/sign-transaction) when you need
supported transaction parsing and [transaction policies](/features/policies/overview).
For supported structured-data parsing, including EIP-712 typed data, see the
[Ethereum signing guidance](/features/networks/ethereum#eip-712).

## Ed25519 hashing

Use `HASH_FUNCTION_NOT_APPLICABLE` with Ed25519 keys. Ed25519 performs hashing as
part of the signature algorithm itself, so there is no separate optional hashing
step for Turnkey to apply. This differs from `HASH_FUNCTION_NO_OP`, which is used
to provide an already hashed ECDSA payload.

Pass the message expected by the Ed25519 protocol, not an ECDSA-style digest. See
[Solana signing](/features/networks/solana) for an integration example and
[RFC 8032, section 5.1](https://datatracker.ietf.org/doc/html/rfc8032#section-5.1)
for the Ed25519 algorithm.

## Request validity

Raw-payload signing is an activity submission. The signed request must meet the
[timestamp validity window](/api-reference/activities/overview#signed-request-validity)
and your organization's [rate limits](/reference/rate-limits).