pubkey compression.

lib/bcoin/ec.js

@@ -86,6 +86,135 @@ ec.publicKeyCreate = function publicKeyCreate(priv, compressed) {
   return new Buffer(priv);
 };
 
+/**
+ * Decode a point.
+ * @param {Buffer} key
+ * @returns {elliptic.Point}
+ */
+
+ec.decodePoint = function decodePoint(key) {
+  var hybrid, point;
+
+  if (key[0] === 0x06 || key[0] === 0x07) {
+    hybrid = key[0];
+    key[0] = 0x04;
+  }
+
+  point = ec.elliptic.curve.decodePoint(key);
+
+  if (hybrid != null)
+    key[0] = hybrid;
+
+  return point;
+};
+
+/**
+ * Compress or decompress public key.
+ * @param {Buffer} pub
+ * @returns {Buffer}
+ */
+
+ec.publicKeyConvert = function(key, compressed) {
+  var point;
+
+  if (secp256k1)
+    return secp256k1.publicKeyConvert(key, compressed);
+
+  switch (key[0]) {
+    case 0x02:
+    case 0x03:
+      if (compressed)
+        return key;
+      point = ec.decodePoint(key);
+      return new Buffer(point.encode('array', false));
+    case 0x04:
+    case 0x06:
+    case 0x07:
+      if (compressed) {
+        point = ec.decodePoint(key);
+        return new Buffer(point.encode('array', true));
+      }
+      return key;
+    default:
+      throw new Error('Bad point format.');
+  }
+};
+
+/**
+ * Compress a public key to coins compression format.
+ * @param {Buffer} key
+ * @returns {Buffer}
+ */
+
+ec.compress = function compress(key) {
+  var out;
+
+  // We can't compress it if it's not valid.
+  if (!ec.publicKeyVerify(key))
+    return;
+
+  switch (key[0]) {
+    case 0x02:
+    case 0x03:
+      // Key is already compressed.
+      out = key;
+      break;
+    case 0x04:
+    case 0x06:
+    case 0x07:
+      // Compress the key normally.
+      out = ec.publicKeyConvert(key, true);
+      // Store the original format (which
+      // may be a hybrid byte) in the hi
+      // 3 bits so we can restore it later.
+      // The hi bits being set also lets us
+      // know that this key was originally
+      // decompressed.
+      out[0] |= key[0] << 2;
+      break;
+    default:
+      throw new Error('Bad point format.');
+  }
+
+  assert(out.length === 33);
+
+  return out;
+};
+
+/**
+ * Decompress a public key from the coins compression format.
+ * @param {Buffer} key
+ * @returns {Buffer}
+ */
+
+ec.decompress = function decompress(key) {
+  var format = key[0] >>> 2;
+  var out;
+
+  assert(key.length === 33);
+
+  // Hi bits are not set. This key
+  // is not meant to be decompressed.
+  if (format === 0)
+    return key;
+
+  // Decompress the key, and off the
+  // low bits so publicKeyConvert
+  // actually understands it.
+  key[0] &= 0x03;
+  out = ec.publicKeyConvert(key, false);
+
+  // Reset the hi bits so as not to
+  // mutate the original buffer.
+  key[0] |= format << 2;
+
+  // Set the original format, which
+  // may have been a hybrid prefix byte.
+  out[0] = format;
+
+  return out;
+};
+
 /**
  * Create an ecdh.
  * @param {Buffer} pub
@@ -211,9 +340,26 @@ ec.verify = function verify(msg, sig, key, historical, high) {
  */
 
 ec.publicKeyVerify = function publicKeyVerify(key) {
+  var result, hybrid;
+
   if (secp256k1)
     return secp256k1.publicKeyVerify(key);
-  return ec.elliptic.keyPair({ pub: key }).validate();
+
+  if (key[0] === 0x06 || key[0] === 0x07) {
+    hybrid = key[0];
+    key[0] = 0x04;
+  }
+
+  try {
+    result = ec.elliptic.keyPair({ pub: key }).validate();
+  } catch (e) {
+    result = false;
+  }
+
+  if (hybrid != null)
+    key[0] = hybrid;
+
+  return result;
 };
 
 /**