comments explaining signing logic.

lib/bcoin/wallet.js

@@ -283,9 +283,18 @@ Wallet.prototype.sign = function sign(tx, type, inputs, off) {
     if (!input.out.tx || !this.ownOutput(input.out.tx))
       return false;
 
+    // Get the previous output's subscript
     var s = input.out.tx.getSubscript(input.out.index);
+
+    // Get the hash of the current tx, minus the other inputs, plus the sighash.
+    // `off` is used here in a case where we have multiple wallet objects
+    // signing the same tx.
     var hash = tx.subscriptHash(off + i, s, type);
+
+    // Sign the transaction with our one input
     var signature = bcoin.ecdsa.sign(hash, this.key).toDER();
+
+    // Add the sighash as a single byte to the signature
     signature = signature.concat(bcoin.protocol.constants.hashType[type]);
 
     // P2PKH and simple tx