Document how to verify the signature of messages and events

docs/.vitepress/config.mjs

@@ -79,6 +79,8 @@ export default defineConfig(withMermaid({
         collapsed: false,
         items: [
           { text: 'Bech32 enc/decoding (NIP-19)', link: '/common-use-cases/bech32-encoding-and-decoding-(NIP-19)' },
+          { text: 'Signing/verifying messages', link: '/common-use-cases/signing-and-verifying-messages' },
+          { text: 'Signing/verifying events', link: '/common-use-cases/signing-and-verifying-events' },
         ]
       },
       {

docs/common-use-cases/signing-and-verifying-events.md

@@ -0,0 +1,50 @@
+# Signing and verifying events
+
+Signing an event in Nostr proves it was sent by the owner of a specific private key.
+
+## Signing an event
+
+To sign an event, use the private key associated with the event's creator. Here's how to sign a message using a
+predefined keypair:
+
+```ruby{14}
+require 'nostr'
+
+private_key = Nostr::PrivateKey.new('67dea2ed018072d675f5415ecfaed7d2597555e202d85b3d65ea4e58d2d92ffa'),
+public_key = Nostr::PublicKey.new('7e7e9c42a91bfef19fa929e5fda1b72e0ebc1a4c1141673e2794234d86addf4e'),
+
+event = Nostr::Event.new(
+  pubkey: public_key.to_s,
+  kind: Nostr::EventKind::TEXT_NOTE,
+  content: 'We did it with security, now we’re going to do it with the economy.',
+  created_at: Time.now.to_i,
+)
+
+# Sign the event with the private key
+event.sign(private_key)
+
+puts "Event ID: #{event.id}"
+puts "Event Signature: #{event.sig}"
+```
+
+## Verifying an event's signature
+
+To verify an event, you must ensure the event's signature is valid. This indicates the event was created by the owner
+of the corresponding public key.
+
+When the event was signed with the private key corresponding to the public key, the `verify_signature` method will
+return `true`.
+
+```ruby
+event.verify_signature # => true
+```
+
+And when the event was not signed with the private key corresponding to the public key, the `verify_signature` method
+will return `false`.
+
+An event without an `id`, `pubkey`, `sig` is considered invalid and will return `false` when calling `verify_signature`.
+
+```ruby
+other_public_key = Nostr::PublicKey.new('10be96d345ed58d923a734560680f1adfd2b1006c28ac93b8e1b032a9a32c6e9')
+event.verify_signature # => false
+```

docs/common-use-cases/signing-and-verifying-messages.md

@@ -0,0 +1,43 @@
+# Signing and verifying messages
+
+Signing a message in Nostr proves it was sent by the owner of a specific private key.
+
+## Signing a message
+
+To sign a message, you'll need a private key. Here's how to sign a message using a predefined keypair:
+
+```ruby{9}
+require 'nostr'
+
+private_key = Nostr::PrivateKey.new('67dea2ed018072d675f5415ecfaed7d2597555e202d85b3d65ea4e58d2d92ffa'),
+public_key = Nostr::PublicKey.new('7e7e9c42a91bfef19fa929e5fda1b72e0ebc1a4c1141673e2794234d86addf4e'),
+
+message = 'We did it with security, now we’re going to do it with the economy.' # The message you want to sign
+
+crypto = Nostr::Crypto.new
+signature = crypto.sign_message(message, private_key)
+signature # => "d7a0aac1fadcddf1aa2949bedfcdf25ce0c1604e648e55d31431fdacbff8e8256f7c2166d98292f80bc5f79105a0b6e8a89236a47d97cf5d0e7cc1ebf34dea5c"
+```
+
+## Verifying a signature
+
+To verify a signature, you need the original message, the public key of the signer, and the signature.
+
+```ruby
+crypto.valid_sig?(message, public_key, signature) # => true
+crypto.check_sig!(message, public_key, signature) # => true
+```
+
+When the message was not signed with the private key corresponding to the public key, the `valid_sig?` method will return `false`.
+
+```ruby
+other_public_key = Nostr::PublicKey.new('10be96d345ed58d923a734560680f1adfd2b1006c28ac93b8e1b032a9a32c6e9')
+crypto.valid_sig?(message, public_key, signature) # => false
+```
+
+And when the message was not signed with the private key corresponding to the public key, the `check_sig!` method will raise an error.
+
+```ruby
+other_public_key = Nostr::PublicKey.new('10be96d345ed58d923a734560680f1adfd2b1006c28ac93b8e1b032a9a32c6e9')
+crypto.check_sig!(message, other_public_key, signature) # => Schnorr::InvalidSignatureError: signature verification failed
+```

docs/getting-started/overview.md

@@ -35,6 +35,7 @@ classDiagram
         serialize()
         to_h()
         sign(private_key)
+        verify_signature()
     }
     class Subscription {
         id