Add support to write V3 signatures

src/packet/signature.js

@@ -175,7 +175,7 @@ Signature.prototype.read = function (bytes) {
 
       break;
     default:
-      throw new Error('Version ' + version + ' of the signature is unsupported.');
+      throw new Error('Version ' + this.version + ' of the signature is unsupported.');
   }
 
   // Two-octet field holding left 16 bits of signed hash value.
@@ -186,11 +186,23 @@ Signature.prototype.read = function (bytes) {
 };
 
 Signature.prototype.write = function () {
-  return this.signatureData +
-    // unhashed subpackets or two octets for zero
-    (this.unhashedSubpackets ? this.unhashedSubpackets : util.writeNumber(0, 2)) +
-    this.signedHashValue +
-    this.signature;
+  var result = '';
+  switch (this.version) {
+    case 3:
+      result += String.fromCharCode(3); // version
+      result += String.fromCharCode(5); // One-octet length of following hashed material.  MUST be 5
+      result += this.signatureData;
+      result += this.issuerKeyId.write();
+      result += String.fromCharCode(this.publicKeyAlgorithm);
+      result += String.fromCharCode(this.hashAlgorithm);
+      break;
+    case 4:
+      result += this.signatureData;
+      result += this.unhashedSubpackets ? this.unhashedSubpackets : util.writeNumber(0, 2);
+      break;
+  }
+  result += this.signedHashValue + this.signature;
+  return result;
 };
 
 /**

test/general/signature.js

@@ -576,4 +576,18 @@ describe("Signature", function() {
     expect(pubKey.users[0].selfCertifications).to.exist;
   });
 
+  it('Write V3 signatures', function() {
+    var pubKey = openpgp.key.readArmored(pub_v3).keys[0];
+    var pubKey2 = openpgp.key.readArmored(pubKey.armor()).keys[0];
+    expect(pubKey2).to.exist;
+    expect(pubKey.users[0].selfCertifications).to.eql(pubKey2.users[0].selfCertifications);
+  });
+
+  it('Write V4 signatures', function() {
+    var pubKey = openpgp.key.readArmored(pub_key_arm2).keys[0];
+    var pubKey2 = openpgp.key.readArmored(pubKey.armor()).keys[0];
+    expect(pubKey2).to.exist;
+    expect(pubKey.users[0].selfCertifications).to.eql(pubKey2.users[0].selfCertifications);
+  });
+
 });