Add low R grinding option

src/ecpair.js

@@ -35,10 +35,25 @@ class ECPair {
             throw new Error('Missing private key');
         return wif.encode(this.network.wif, this.__D, this.compressed);
     }
-    sign(hash) {
+    sign(hash, lowR = false) {
         if (!this.__D)
             throw new Error('Missing private key');
-        return ecc.sign(hash, this.__D);
+        if (lowR === false) {
+            return ecc.sign(hash, this.__D);
+        }
+        else {
+            let sig = ecc.sign(hash, this.__D);
+            const extraData = Buffer.alloc(32, 0);
+            let counter = 0;
+            // if first try is lowR, skip the loop
+            // for second try and on, add extra entropy counting up
+            while (sig[0] > 0x7f) {
+                counter++;
+                extraData.writeUIntLE(counter, 0, 6);
+                sig = ecc.signWithEntropy(hash, this.__D, extraData);
+            }
+            return sig;
+        }
     }
     verify(hash, signature) {
         return ecc.verify(hash, this.publicKey, signature);

ts_src/ecpair.ts

@@ -61,9 +61,23 @@ class ECPair implements ECPairInterface {
     return wif.encode(this.network.wif, this.__D, this.compressed);
   }
 
-  sign(hash: Buffer): Buffer {
+  sign(hash: Buffer, lowR: boolean = false): Buffer {
     if (!this.__D) throw new Error('Missing private key');
-    return ecc.sign(hash, this.__D);
+    if (lowR === false) {
+      return ecc.sign(hash, this.__D);
+    } else {
+      let sig = ecc.sign(hash, this.__D);
+      const extraData = Buffer.alloc(32, 0);
+      let counter = 0;
+      // if first try is lowR, skip the loop
+      // for second try and on, add extra entropy counting up
+      while (sig[0] > 0x7f) {
+        counter++;
+        extraData.writeUIntLE(counter, 0, 6);
+        sig = ecc.signWithEntropy(hash, this.__D, extraData);
+      }
+      return sig;
+    }
   }
 
   verify(hash: Buffer, signature: Buffer): Buffer {

types/ecpair.d.ts

@@ -24,7 +24,7 @@ declare class ECPair implements ECPairInterface {
     readonly privateKey: Buffer | undefined;
     readonly publicKey: Buffer | undefined;
     toWIF(): string;
-    sign(hash: Buffer): Buffer;
+    sign(hash: Buffer, lowR?: boolean): Buffer;
     verify(hash: Buffer, signature: Buffer): Buffer;
 }
 declare function fromPrivateKey(buffer: Buffer, options?: ECPairOptions): ECPair;