# Signal Protocol Specifications

**Canonical:** https://apis.io/apis/signal/signal-protocol-specifications/  
**Provider:** Signal — https://apis.io/providers/signal/  
**Documentation:** https://signal.org/docs/

Signal Protocol Specifications is one of 14 APIs that [Signal](https://apis.io/providers/signal/) publishes on the [APIs.io](https://apis.io/) network. Tagged areas include Encryption, Messaging, Cryptography, Security, and Protocols. The published artifact set on APIs.io includes API documentation.

The Signal Protocol Specifications define the core cryptographic protocols that underpin Signal's end-to-end encrypted messaging. These include the X3DH (Extended Triple Diffie-Hellman) key agreement protocol for establishing shared secrets between parties, the Double Ratchet Algorithm for deriving new encryption keys per message, the PQXDH (Post-Quantum Extended Diffie-Hellman) protocol for quantum-resistant key agreement, and XEdDSA for EdDSA-compatible signature schemes. These specifications are published independently so they can be adopted by other projects beyond Signal itself.

## Machine-readable artifacts (2)

- **Documentation** — https://signal.org/docs/
- **APIsJSON** — https://raw.githubusercontent.com/api-evangelist/signal/refs/heads/main/apis.yml

## Other Signal APIs (12)

- [Signal libsignal SDK](https://apis.io/apis/signal/signal-libsignal-sdk/)
- [Signal Android SDK](https://apis.io/apis/signal/signal-android-sdk/)
- [Signal iOS SDK](https://apis.io/apis/signal/signal-ios-sdk/)
- [Signal Desktop SDK](https://apis.io/apis/signal/signal-desktop-sdk/)
- [Signal Accounts API](https://apis.io/apis/signal/signal-accounts-api/)
- [Signal Attachments API](https://apis.io/apis/signal/signal-attachments-api/)
- [Signal Certificates API](https://apis.io/apis/signal/signal-certificates-api/)
- [Signal Devices API](https://apis.io/apis/signal/signal-devices-api/)
- [Signal Keys API](https://apis.io/apis/signal/signal-keys-api/)
- [Signal Messages API](https://apis.io/apis/signal/signal-messages-api/)
- [Signal Profiles API](https://apis.io/apis/signal/signal-profiles-api/)
- [Signal Registration API](https://apis.io/apis/signal/signal-registration-api/)

## Tags

Encryption, Messaging, Cryptography, Security, Protocols

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/signal/signal-protocol-specifications/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/signal/.