Implement NIP-04: Encrypted Direct Messages

spec/nostr/crypto_spec.rb

@@ -30,4 +30,50 @@ RSpec.describe Nostr::Crypto do
       end
     end
   end
+
+  describe '#encrypt_text' do
+    let(:sender_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '8a9d69c56e3c691bec8f9565e4dcbe38ae1d88fffeec3ce66b9f47558a3aa8ca',
+        private_key: '3185a47e3802f956ca5a2b4ea606c1d51c7610f239617e8f0f218d55bdf2b757'
+      )
+    end
+
+    let(:recipient_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '6c31422248998e300a1a457167565da7d15d0da96651296ee2791c29c11b6aa0',
+        private_key: '22cea01c33eccf30fdd54cb6728f814f6de00c778aafd721e017f4582545f9cf'
+      )
+    end
+
+    it 'encrypts plain text' do
+      encrypted_text = crypto.encrypt_text(sender_keypair.private_key, recipient_keypair.public_key, 'Twitter Files')
+      decrypted_text = crypto.decrypt_text(recipient_keypair.private_key, sender_keypair.public_key, encrypted_text)
+
+      expect(decrypted_text).to eq('Twitter Files')
+    end
+  end
+
+  describe '#descrypt_text' do
+    let(:sender_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '8a9d69c56e3c691bec8f9565e4dcbe38ae1d88fffeec3ce66b9f47558a3aa8ca',
+        private_key: '3185a47e3802f956ca5a2b4ea606c1d51c7610f239617e8f0f218d55bdf2b757'
+      )
+    end
+
+    let(:recipient_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '6c31422248998e300a1a457167565da7d15d0da96651296ee2791c29c11b6aa0',
+        private_key: '22cea01c33eccf30fdd54cb6728f814f6de00c778aafd721e017f4582545f9cf'
+      )
+    end
+
+    it 'decrypts an encrypted text' do
+      encrypted_text = crypto.encrypt_text(sender_keypair.private_key, recipient_keypair.public_key, 'Twitter Files')
+      decrypted_text = crypto.decrypt_text(recipient_keypair.private_key, sender_keypair.public_key, encrypted_text)
+
+      expect(decrypted_text).to eq('Twitter Files')
+    end
+  end
 end

spec/nostr/event_kind_spec.rb

@@ -26,4 +26,10 @@ RSpec.describe Nostr::EventKind do
       expect(described_class::CONTACT_LIST).to eq(3)
     end
   end
+
+  describe '::ENCRYPTED_DIRECT_MESSAGE' do
+    it 'is an integer' do
+      expect(described_class::ENCRYPTED_DIRECT_MESSAGE).to eq(4)
+    end
+  end
 end

spec/nostr/events/encrypted_direct_message_spec.rb

@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Nostr::Events::EncryptedDirectMessage do
+  describe '.new' do
+    let(:sender_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '8a9d69c56e3c691bec8f9565e4dcbe38ae1d88fffeec3ce66b9f47558a3aa8ca',
+        private_key: '3185a47e3802f956ca5a2b4ea606c1d51c7610f239617e8f0f218d55bdf2b757'
+      )
+    end
+
+    let(:recipient_keypair) do
+      Nostr::KeyPair.new(
+        public_key: '6c31422248998e300a1a457167565da7d15d0da96651296ee2791c29c11b6aa0',
+        private_key: '22cea01c33eccf30fdd54cb6728f814f6de00c778aafd721e017f4582545f9cf'
+      )
+    end
+
+    let(:crypto) { Nostr::Crypto.new }
+
+    it 'creates an instance of an encrypted private message event that can be decrypted by its recipient' do
+      encrypted_direct_message = described_class.new(
+        sender_private_key: sender_keypair.private_key,
+        recipient_public_key: recipient_keypair.public_key,
+        plain_text: 'Your feedback is appreciated, now pay $8'
+      )
+
+      plain_text = crypto.decrypt_text(
+        recipient_keypair.private_key,
+        sender_keypair.public_key,
+        encrypted_direct_message.content
+      )
+
+      aggregate_failures do
+        expect(encrypted_direct_message.content).not_to eq(plain_text)
+        expect(plain_text).to eq('Your feedback is appreciated, now pay $8')
+      end
+    end
+
+    it 'adds a reference to the recipient in the tags' do
+      encrypted_direct_message = described_class.new(
+        sender_private_key: sender_keypair.private_key,
+        recipient_public_key: recipient_keypair.public_key,
+        plain_text: 'Your feedback is appreciated, now pay $8'
+      )
+
+      expect(encrypted_direct_message.tags).to eq([['p', recipient_keypair.public_key]])
+    end
+
+    context 'when previous_direct_message is omitted' do
+      it 'does not add a reference to a previous message' do
+        encrypted_direct_message = described_class.new(
+          sender_private_key: sender_keypair.private_key,
+          recipient_public_key: recipient_keypair.public_key,
+          plain_text: 'Your feedback is appreciated, now pay $8'
+        )
+
+        expect(encrypted_direct_message.tags).to eq([['p', recipient_keypair.public_key]])
+      end
+    end
+
+    context 'when previous_direct_message is given' do
+      let(:previous_direct_message_id) { 'ccf9fdf3e1466d7c20969c71ec98defcf5f54aee088513e1b73ccb7bd770d460' }
+
+      it 'adds a reference to a previous message' do
+        encrypted_direct_message = described_class.new(
+          sender_private_key: sender_keypair.private_key,
+          recipient_public_key: recipient_keypair.public_key,
+          plain_text: 'Your feedback is appreciated, now pay $8',
+          previous_direct_message: previous_direct_message_id
+        )
+
+        expect(encrypted_direct_message.tags).to eq(
+          [
+            ['p', recipient_keypair.public_key],
+            ['e', previous_direct_message_id]
+          ]
+        )
+      end
+    end
+  end
+end