fix(identity)!: update type of private key (#803)

* fix(identity)!: update type of private key The new types support buffers and text, so that there is less ambiguity on strings. * refactor(identity): use base64 as encoding for exported priv keys re #799 * Update packages/identity/src/index.ts Co-authored-by: Andrew Twyman <artwyman@users.noreply.github.com> * test(identity): add more tests re #799 --------- Co-authored-by: Andrew Twyman <artwyman@users.noreply.github.com>
semaphore-protocol · Jun 18, 2024 · 3572f44 · 3572f44
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diff --git a/packages/identity/README.md b/packages/identity/README.md
@@ -84,6 +84,28 @@ const { privateKey, publicKey, commitment } = new Identity()
 const identity = new Identity("your-private-key")
 ```
 
+\# **identity.export**(): _string_
+
+```typescript
+import { Identity } from "@semaphore-protocol/identity"
+
+const identity = new Identity()
+
+const privateKey = identity.export()
+```
+
+\# **identity.import**(privateKey: _string_): _Identity_
+
+```typescript
+import { Identity } from "@semaphore-protocol/identity"
+
+const identity = new Identity()
+
+const privateKey = identity.export()
+
+const identity2 = Identity.import(privateKey)
+```
+
 \# **identity.signMessage**(message: _BigNumberish_): _Signature\<string>_
 
 ```typescript

diff --git a/packages/identity/package.json b/packages/identity/package.json
@@ -40,8 +40,8 @@
     },
     "dependencies": {
         "@zk-kit/baby-jubjub": "1.0.1",
-        "@zk-kit/eddsa-poseidon": "1.0.1",
-        "@zk-kit/utils": "1.0.0",
+        "@zk-kit/eddsa-poseidon": "1.0.2",
+        "@zk-kit/utils": "1.2.0",
         "poseidon-lite": "0.2.0"
     }
 }
diff --git a/packages/identity/src/index.ts b/packages/identity/src/index.ts
@@ -1,9 +1,8 @@
 import type { Point } from "@zk-kit/baby-jubjub"
 import { EdDSAPoseidon, Signature, signMessage, verifySignature } from "@zk-kit/eddsa-poseidon"
 import type { BigNumberish } from "@zk-kit/utils"
-import { hexadecimalToBuffer } from "@zk-kit/utils/conversions"
-import { requireString } from "@zk-kit/utils/error-handlers"
-import { isHexadecimal } from "@zk-kit/utils/type-checks"
+import { base64ToBuffer, bufferToBase64, textToBase64 } from "@zk-kit/utils/conversions"
+import { isString } from "@zk-kit/utils/type-checks"
 import { poseidon2 } from "poseidon-lite/poseidon2"
 
 /**
@@ -13,12 +12,11 @@ import { poseidon2 } from "poseidon-lite/poseidon2"
  * and {@link https://www.poseidon-hash.info | Poseidon} for signatures.
  * In addition, the commitment, i.e. the hash of the public key, is used to represent
  * Semaphore identities in groups, adding an additional layer of privacy and security.
- * The private key of the identity is stored as a hexadecimal string or text.
- * The other attributes are stored as stringified bigint.
+ * The private key of the identity can be exported as a base64 string.
  */
 export class Identity {
     // The EdDSA private key, passed as a parameter or generated randomly.
-    private _privateKey: string
+    private _privateKey: string | Buffer | Uint8Array
     // The secret scalar derived from the private key.
     // It is used in circuits to derive the public key.
     private _secretScalar: bigint
@@ -28,9 +26,8 @@ export class Identity {
     private _commitment: bigint
 
     /**
-     * Initializes the class attributes based on a given private key, which must be a hexadecimal string or a text.
-     * Hexadecimal strings must not start with '0x' or '0X'.
-     * If the private key is not passed as a parameter, a random hexadecimal key will be generated.
+     * Initializes the class attributes based on a given private key, which must be text or a buffer.
+     * If the private key is not passed as a parameter, a random private key will be generated.
      * The EdDSAPoseidon class is used to generate the secret scalar and the public key.
      * Additionally, the constructor computes a commitment of the public key using a hash function (Poseidon).
      *
@@ -43,35 +40,20 @@ export class Identity {
      *
      * @param privateKey The private key used to derive the public key (hexadecimal or string).
      */
-    constructor(privateKey?: string) {
-        let eddsa: EdDSAPoseidon
-
-        if (privateKey) {
-            requireString(privateKey, "privateKey")
-
-            this._privateKey = privateKey
-
-            if (isHexadecimal(privateKey, false)) {
-                eddsa = new EdDSAPoseidon(hexadecimalToBuffer(privateKey))
-            } else {
-                eddsa = new EdDSAPoseidon(privateKey)
-            }
-        } else {
-            eddsa = new EdDSAPoseidon()
-
-            this._privateKey = eddsa.privateKey as string
-        }
+    constructor(privateKey?: string | Buffer | Uint8Array) {
+        const eddsa = new EdDSAPoseidon(privateKey)
 
+        this._privateKey = eddsa.privateKey
         this._secretScalar = eddsa.secretScalar
         this._publicKey = eddsa.publicKey
         this._commitment = poseidon2(this._publicKey)
     }
 
     /**
      * Returns the private key.
-     * @returns The private key as a string (hexadecimal or text).
+     * @returns The private key as a buffer or text.
      */
-    public get privateKey(): string {
+    public get privateKey(): string | Buffer | Uint8Array {
         return this._privateKey
     }
 
@@ -99,6 +81,28 @@ export class Identity {
         return this._commitment
     }
 
+    /**
+     * Returns the private key encoded as a base64 string.
+     * @returns The private key as a base64 string.
+     */
+    public export(): string {
+        if (isString(this._privateKey)) {
+            return textToBase64(this._privateKey as string)
+        }
+
+        return bufferToBase64(this.privateKey as Buffer | Uint8Array)
+    }
+
+    /**
+     * Returns a Semaphore identity based on a private key encoded as a base64 string.
+     * The private key will be converted to a buffer, regardless of its original type.
+     * @param privateKey The private key as a base64 string.
+     * @returns The Semaphore identity.
+     */
+    static import(privateKey: string): Identity {
+        return new Identity(base64ToBuffer(privateKey))
+    }
+
     /**
      * Generates a signature for a given message using the private key.
      * This method demonstrates how to sign a message and could be used
@@ -112,11 +116,7 @@ export class Identity {
      * @returns A {@link https://zkkit.pse.dev/types/_zk_kit_eddsa_poseidon.Signature.html | Signature} object containing the signature components.
      */
     public signMessage(message: BigNumberish): Signature<bigint> {
-        const privateKey = isHexadecimal(this.privateKey, false)
-            ? hexadecimalToBuffer(this.privateKey)
-            : this.privateKey
-
-        return signMessage(privateKey, message)
+        return signMessage(this.privateKey, message)
     }
 
     /**

diff --git a/packages/identity/tests/index.test.ts b/packages/identity/tests/index.test.ts
@@ -1,43 +1,111 @@
+import { derivePublicKey, deriveSecretScalar } from "@zk-kit/eddsa-poseidon"
+import { poseidon2 } from "poseidon-lite"
 import { Identity } from "../src"
 
 describe("Identity", () => {
     const privateKeyText = "secret"
-    const privateKeyHexadecimal = "dd998334940df8931b76d899fdb189415f7ff4280599f03a7574725a166aad7d"
+    const privateKeyBuffer = Buffer.from("another secret")
 
     describe("# Identity", () => {
         it("Should create an identity with a random secret (private key)", () => {
             const identity = new Identity()
+            const privateKey = Buffer.from(identity.privateKey)
 
-            expect(typeof identity.privateKey).toBe("string")
-            expect(identity.privateKey).toHaveLength(64)
-            expect(typeof identity.secretScalar).toBe("bigint")
-            expect(identity.publicKey).toHaveLength(2)
-            expect(typeof identity.commitment).toBe("bigint")
+            expect(identity.privateKey).toHaveLength(32)
+            expect(identity.secretScalar).toBe(deriveSecretScalar(privateKey))
+            expect(identity.publicKey).toStrictEqual(derivePublicKey(privateKey))
+            expect(identity.commitment).toBe(poseidon2(identity.publicKey))
         })
 
-        it("Should create deterministic identities from a secret text (private key)", () => {
+        it("Should create a deterministic identity from a secret text (private key)", () => {
             const identity = new Identity(privateKeyText)
 
-            expect(typeof identity.privateKey).toBe("string")
-            expect(typeof identity.secretScalar).toBe("bigint")
-            expect(identity.publicKey).toHaveLength(2)
-            expect(typeof identity.commitment).toBe("bigint")
+            expect(identity.secretScalar).toBe(deriveSecretScalar(privateKeyText))
+            expect(identity.publicKey).toStrictEqual(derivePublicKey(privateKeyText))
+            expect(identity.commitment).toBe(poseidon2(identity.publicKey))
         })
 
-        it("Should create deterministic identities from a secret hexadecimal (private key)", () => {
-            const identity = new Identity(privateKeyHexadecimal)
+        it("Should create a deterministic identity from a secret buffer (private key)", () => {
+            const identity = new Identity(privateKeyBuffer)
 
-            expect(typeof identity.privateKey).toBe("string")
-            expect(identity.privateKey).toHaveLength(64)
-            expect(typeof identity.secretScalar).toBe("bigint")
-            expect(identity.publicKey).toHaveLength(2)
-            expect(typeof identity.commitment).toBe("bigint")
+            expect(identity.secretScalar).toBe(deriveSecretScalar(privateKeyBuffer))
+            expect(identity.publicKey).toStrictEqual(derivePublicKey(privateKeyBuffer))
+            expect(identity.commitment).toBe(poseidon2(identity.publicKey))
+        })
+
+        it("Should create the same identity if the private key is the same", () => {
+            const identity = new Identity()
+
+            const identity2 = new Identity(identity.privateKey)
+
+            expect(identity.privateKey).toStrictEqual(identity2.privateKey)
+            expect(identity.secretScalar).toBe(identity2.secretScalar)
+            expect(identity.publicKey).toStrictEqual(identity2.publicKey)
+            expect(identity.commitment).toBe(identity2.commitment)
         })
 
         it("Should throw an error if the private key is not a string", () => {
             const fun = () => new Identity(32 as any)
 
-            expect(fun).toThrow("Parameter 'privateKey' is not a string, received type: number")
+            expect(fun).toThrow("Parameter 'privateKey' is none of the following types: Buffer, Uint8Array, string")
+        })
+    })
+
+    describe("# export", () => {
+        it("Should export an identity where the private key is a buffer", () => {
+            const identity = new Identity(privateKeyBuffer)
+
+            const privateKey = identity.export()
+
+            expect(typeof privateKey).toBe("string")
+            expect(Buffer.from(privateKey, "base64")).toStrictEqual(privateKeyBuffer)
+        })
+
+        it("Should export an identity where the private key is text", () => {
+            const identity = new Identity(privateKeyBuffer)
+
+            const privateKey = identity.export()
+
+            expect(typeof privateKey).toBe("string")
+            expect(Buffer.from(privateKey, "base64")).toStrictEqual(privateKeyBuffer)
+        })
+    })
+
+    describe("# import", () => {
+        it("Should import an identity with a private key of buffer type", () => {
+            const identity = new Identity(privateKeyBuffer)
+            const privateKey = identity.export()
+
+            const identity2 = Identity.import(privateKey)
+
+            expect(identity2.privateKey).toStrictEqual(identity.privateKey)
+            expect(identity2.secretScalar).toBe(identity.secretScalar)
+            expect(identity2.publicKey).toStrictEqual(identity.publicKey)
+            expect(identity2.commitment).toBe(identity.commitment)
+        })
+
+        it("Should import an identity with a private key of text type", () => {
+            const identity = new Identity(privateKeyText)
+            const privateKey = identity.export()
+
+            const identity2 = Identity.import(privateKey)
+
+            expect(identity2.privateKey).toStrictEqual(Buffer.from(identity.privateKey))
+            expect(identity2.secretScalar).toBe(identity.secretScalar)
+            expect(identity2.publicKey).toStrictEqual(identity.publicKey)
+            expect(identity2.commitment).toBe(identity.commitment)
+        })
+
+        it("Should import an identity generated from a random private key", () => {
+            const identity = new Identity()
+            const privateKey = identity.export()
+
+            const identity2 = Identity.import(privateKey)
+
+            expect(identity2.privateKey).toStrictEqual(Buffer.from(identity.privateKey))
+            expect(identity2.secretScalar).toBe(identity.secretScalar)
+            expect(identity2.publicKey).toStrictEqual(identity.publicKey)
+            expect(identity2.commitment).toBe(identity.commitment)
         })
     })
 
@@ -63,7 +131,7 @@ describe("Identity", () => {
         })
 
         it("Should verify a signature with hexadecimal private key", () => {
-            const identity = new Identity(privateKeyHexadecimal)
+            const identity = new Identity(privateKeyBuffer)
 
             const signature = identity.signMessage("message")
 

diff --git a/yarn.lock b/yarn.lock
@@ -6394,8 +6394,8 @@ __metadata:
     "@rollup/plugin-node-resolve": "npm:^15.2.3"
     "@rollup/plugin-typescript": "npm:^11.1.6"
     "@zk-kit/baby-jubjub": "npm:1.0.1"
-    "@zk-kit/eddsa-poseidon": "npm:1.0.1"
-    "@zk-kit/utils": "npm:1.0.0"
+    "@zk-kit/eddsa-poseidon": "npm:1.0.2"
+    "@zk-kit/utils": "npm:1.2.0"
     poseidon-lite: "npm:0.2.0"
     rimraf: "npm:^5.0.5"
     rollup: "npm:^4.12.0"
@@ -8487,14 +8487,14 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@zk-kit/eddsa-poseidon@npm:1.0.1":
-  version: 1.0.1
-  resolution: "@zk-kit/eddsa-poseidon@npm:1.0.1"
+"@zk-kit/eddsa-poseidon@npm:1.0.2":
+  version: 1.0.2
+  resolution: "@zk-kit/eddsa-poseidon@npm:1.0.2"
   dependencies:
     "@zk-kit/baby-jubjub": "npm:1.0.1"
     "@zk-kit/utils": "npm:1.0.0"
     buffer: "npm:6.0.3"
-  checksum: 10/337db4a73bd58680e462b6a82f95321406b3cffce7dce0413f7c857159798b8d85120750de5f5e4c7f2bcc102a02a5e3145302aeb9110a3b6172e6bd3bc29f43
+  checksum: 10/4b4e984a96c5dbc95a8cf36ceb8b3712e37291c1473d01b0e22c15a33311e9cf88c86175d878dacda1852cc905cd2074aaa76defeaed33490be3964ca7a53372
   languageName: node
   linkType: hard
 
@@ -8525,6 +8525,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@zk-kit/utils@npm:1.2.0":
+  version: 1.2.0
+  resolution: "@zk-kit/utils@npm:1.2.0"
+  dependencies:
+    buffer: "npm:^6.0.3"
+  checksum: 10/4c0b37d64b28a6cc33c901a0c59325b1fe9c31e6519eaefe4aa6028ae9cb85e97f047976942875face030a1835d5c955ea546d7dc4fcf9d35df79192ee2502f3
+  languageName: node
+  linkType: hard
+
 "JSONStream@npm:1.3.2":
   version: 1.3.2
   resolution: "JSONStream@npm:1.3.2"