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Documentation Index

Fetch the complete documentation index at: https://docs.portalhq.io/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

Presignatures allow you to split the MPC signing protocol into two phases:
  1. Pre-computation phase — Generate a presignature ahead of time using the presign endpoint.
  2. Signing phase — Pass the presignature to a sign, raw sign, or send asset endpoint to complete the signature faster.
By front-loading part of the cryptographic computation, the signing step completes faster. This is useful when you need lower-latency signing at transaction time or want to prepare signatures in advance for time-sensitive operations.

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How It Works

The Enclave MPC API supports two presignature storage modes:
ModeHow it works
Client-storedThe presign endpoint returns an opaque data blob. Your application stores it and later passes it as presignature in a signing request.
Portal-managedPortal stores the encrypted client presignature payload. Your application stores only the returned id and later passes it as presignatureId in a signing request.
In both modes, the signing endpoint uses the pre-computed data to complete the MPC protocol faster. Presignatures workflow

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Key Details

PropertyDetails
Supported curvesSECP256K1 (EVM, Bitcoin). ED25519 (Solana) support coming soon.
Default expiration7 days from creation
Maximum expiration365 days from creation
Active limit100 presignatures per client
UsageSingle-use — each presignature can only be used for one signing operation

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Use Cases

  • Low-latency signing — Pre-compute during idle time so that user-facing sign requests complete faster.
  • Batch preparation — Generate multiple presignatures in advance for a batch of upcoming transactions.
  • Time-sensitive transactions — Prepare presignatures before a deadline so signing is fast when needed.

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Compatible Endpoints

Presignatures can be used with the following Enclave MPC API endpoints:
  • Sign (POST /v1/sign) — RPC-based signing (e.g., eth_sendTransaction)
  • Raw Sign (POST /v1/raw/sign/SECP256K1) — Sign a hex digest string
  • Send Assets (POST /v1/assets/send) — High-level token transfer
Presignatures currently only support the SECP256K1 curve. ED25519 (Solana) support is coming soon.

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Best Practices

  • For client-stored presignatures, store the id and expiresAt alongside the data value. While the id is not required for signing, it is useful for bookkeeping and may be needed when communicating with Portal support.
  • For Portal-managed presignatures, store the id and expiresAt so you can pass the id as presignatureId and clean up expired presignatures.
  • Discard expired presignatures — set up a regular process to check expiresAt timestamps and clean up expired entries so you stay within the 100 active presignature limit.

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SDK behavior

The SDK manages presignatures automatically when you enable the usePresignatures feature flag. With the flag enabled, the SDK generates presignatures in the background and uses them during signing (e.g. portal.request() or send-asset flows) to improve latency

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Next Steps

Ready to use presignatures? Choose your platform: