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contextvm-docs/src/content/docs/signer/nostr-signer-interface.md
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NostrSigner Interface An interface for signing Nostr events.

NostrSigner Interface

The NostrSigner interface is a central component of the @contextvm/sdk, defining the standard for cryptographic signing operations. Every Nostr event must be signed by a private key to be considered valid, and this interface provides a consistent, pluggable way to handle this requirement.

Purpose and Design

The primary purpose of the NostrSigner is to abstract the process of event signing. By depending on this interface rather than a concrete implementation, the SDK's transports and other components can remain agnostic about how and where private keys are stored and used.

This design offers several key benefits:

  • Security: Private keys can be managed in secure environments (e.g., web extensions, hardware wallets, dedicated signing services) without exposing them to the application logic.
  • Flexibility: Developers can easily swap out the default signer with a custom implementation that meets their specific needs.
  • Modularity: The signing logic is decoupled from the communication logic, leading to a cleaner, more maintainable codebase.

Interface Definition

The NostrSigner interface is defined in core/interfaces.ts.

export interface NostrSigner {
  getPublicKey(): Promise<string>;
  signEvent(event: EventTemplate): Promise<NostrEvent>;

  // Optional NIP-04 encryption support (deprecated)
  nip04?: {
    encrypt: (pubkey: string, plaintext: string) => Promise<string>;
    decrypt: (pubkey: string, ciphertext: string) => Promise<string>;
  };

  // Optional NIP-44 encryption support
  nip44?: {
    encrypt: (pubkey: string, plaintext: string) => Promise<string>;
    decrypt: (pubkey: string, ciphertext: string) => Promise<string>;
  };
}
  • getPublicKey(): Asynchronously returns the public key corresponding to the signer's private key.
  • signEvent(event): Takes an unsigned Nostr event, signs it, and returns the signature.
  • nip04: (Deprecated) Provides NIP-04 encryption support.
  • nip44: Provides NIP-44 encryption support.

Any class that implements this interface can be used as a signer throughout the SDK.

Implementations

The SDK provides a default implementation for common use cases and allows for custom implementations for advanced scenarios.

  • PrivateKeySigner: The default implementation, which takes a raw private key string and performs signing operations locally.
  • Custom Signer Development: For creating custom signers that integrate with key management systems, such as hardware wallets or remote signing services.

Next Steps