Merge pull request #295 from semaphore-protocol/feat/identity-getter

New identity secret attribute and getter

Former-commit-id: 2af0af9

Author: cedoor

packages/identity/src/identity.test.ts

@@ -19,6 +19,7 @@ describe("Identity", () => {
 
             expect(identity1.trapdoor).not.toBe(identity2.getTrapdoor())
             expect(identity1.nullifier).not.toBe(identity2.getNullifier())
+            expect(identity1.secret).not.toBe(identity2.getSecret())
             expect(identity1.commitment).not.toBe(identity2.getCommitment())
         })
 
@@ -82,8 +83,18 @@ describe("Identity", () => {
         })
     })
 
-    describe("# generateCommitment", () => {
-        it("Should generate an identity commitment", () => {
+    describe("# getSecret", () => {
+        it("Should return an identity secret", () => {
+            const { secret } = new Identity("message")
+
+            expect(secret.toString()).toBe(
+                "17452394798940441025978193762953691632066258438336130543532009665042636950194"
+            )
+        })
+    })
+
+    describe("# getCommitment", () => {
+        it("Should return an identity commitment", () => {
             const { commitment } = new Identity("message")
 
             expect(commitment.toString()).toBe(

packages/identity/src/identity.ts

@@ -1,11 +1,14 @@
 import { BigNumber } from "@ethersproject/bignumber"
 import hash from "js-sha512"
+import { poseidon1 } from "poseidon-lite/poseidon1"
+import { poseidon2 } from "poseidon-lite/poseidon2"
 import checkParameter from "./checkParameter"
-import { generateCommitment, genRandomNumber, isJsonArray } from "./utils"
+import { genRandomNumber, isJsonArray } from "./utils"
 
 export default class Identity {
     private _trapdoor: bigint
     private _nullifier: bigint
+    private _secret: bigint
     private _commitment: bigint
 
     /**
@@ -16,7 +19,8 @@ export default class Identity {
         if (identityOrMessage === undefined) {
             this._trapdoor = genRandomNumber()
             this._nullifier = genRandomNumber()
-            this._commitment = generateCommitment(this._nullifier, this._trapdoor)
+            this._secret = poseidon2([this._nullifier, this._trapdoor])
+            this._commitment = poseidon1([this._secret])
 
             return
         }
@@ -25,10 +29,11 @@ export default class Identity {
 
         if (!isJsonArray(identityOrMessage)) {
             const h = hash.sha512(identityOrMessage).padStart(128, "0")
-            // alt_bn128 is 253.6 bits, so we can safely use 253 bits
+            // alt_bn128 is 253.6 bits, so we can safely use 253 bits.
             this._trapdoor = BigInt(`0x${h.slice(64)}`) >> BigInt(3)
             this._nullifier = BigInt(`0x${h.slice(0, 64)}`) >> BigInt(3)
-            this._commitment = generateCommitment(this._nullifier, this._trapdoor)
+            this._secret = poseidon2([this._nullifier, this._trapdoor])
+            this._commitment = poseidon1([this._secret])
 
             return
         }
@@ -37,7 +42,8 @@ export default class Identity {
 
         this._trapdoor = BigNumber.from(trapdoor).toBigInt()
         this._nullifier = BigNumber.from(nullifier).toBigInt()
-        this._commitment = generateCommitment(this._nullifier, this._trapdoor)
+        this._secret = poseidon2([this._nullifier, this._trapdoor])
+        this._commitment = poseidon1([this._secret])
     }
 
     /**
@@ -72,6 +78,22 @@ export default class Identity {
         return this._nullifier
     }
 
+    /**
+     * Returns the identity secret.
+     * @returns The identity secret.
+     */
+    public get secret(): bigint {
+        return this._secret
+    }
+
+    /**
+     * Returns the identity secret.
+     * @returns The identity secret.
+     */
+    public getSecret(): bigint {
+        return this._secret
+    }
+
     /**
      * Returns the identity commitment.
      * @returns The identity commitment.

packages/identity/src/utils.ts

@@ -1,7 +1,5 @@
 import { BigNumber } from "@ethersproject/bignumber"
 import { randomBytes } from "@ethersproject/random"
-import { poseidon1 } from "poseidon-lite/poseidon1"
-import { poseidon2 } from "poseidon-lite/poseidon2"
 
 /**
  * Generates a random big number.
@@ -12,16 +10,6 @@ export function genRandomNumber(numberOfBytes = 31): bigint {
     return BigNumber.from(randomBytes(numberOfBytes)).toBigInt()
 }
 
-/**
- * Generates the identity commitment from trapdoor and nullifier.
- * @param nullifier The identity nullifier.
- * @param trapdoor The identity trapdoor.
- * @returns identity commitment
- */
-export function generateCommitment(nullifier: bigint, trapdoor: bigint): bigint {
-    return poseidon1([poseidon2([nullifier, trapdoor])])
-}
-
 /**
  * Checks if a string is a JSON.
  * @param jsonString The JSON string.