Add isSignatureValid method and tests for it

2 files changed, 30 insertions, 3 deletions

diff --git a/src/ts/0x.js.ts b/src/ts/0x.js.ts
index 95446ad74..6d6d5fed6 100644
--- a/src/ts/0x.js.ts
+++ b/src/ts/0x.js.ts
@@ -1,6 +1,32 @@
+import * as ethUtil from 'ethereumjs-util';
+
+/**
+ * Elliptic Curve signature
+ */
+export interface ECSignature {
+    v: number;
+    r: string;
+    s: string;
+}
+
+export type ETHAddress = string;
+
 export class ZeroEx {
-    /** Verifies the signature */
-    public verifySignature() {
-        // TODO
+    /**
+     * Checks if the signature is valid
+     */
+    public static isValidSignature(data: string, signature: ECSignature, signer: ETHAddress): boolean {
+        const dataBuff = ethUtil.toBuffer(data);
+        const msgHashBuff = ethUtil.hashPersonalMessage(dataBuff);
+        try {
+            const pubKey = ethUtil.ecrecover(msgHashBuff,
+                signature.v,
+                ethUtil.toBuffer(signature.r),
+                ethUtil.toBuffer(signature.s));
+            const retrievedAddress = ethUtil.bufferToHex(ethUtil.pubToAddress(pubKey));
+            return retrievedAddress === signer;
+        } catch (err) {
+            return false;
+        }
     }
 }
diff --git a/src/ts/globals.d.ts b/src/ts/globals.d.ts
new file mode 100644
index 000000000..99f9cf50b
--- /dev/null
+++ b/src/ts/globals.d.ts
@@ -0,0 +1 @@
+declare module 'ethereumjs-util';