diff --git a/packages/agent/src/auth.ts b/packages/agent/src/auth.ts
index d4ed8674..9c4c57d0 100644
--- a/packages/agent/src/auth.ts
+++ b/packages/agent/src/auth.ts
@@ -28,7 +28,8 @@ export type Signature = ArrayBuffer & { __signature__: void };
  */
 export interface PublicKey {
   toDer(): DerEncodedPublicKey;
-  // rawKey and derKey are optional for backwards compatibility.
+  // rawKey, toRaw, and derKey are optional for backwards compatibility.
+  toRaw?(): ArrayBuffer;
   rawKey?: ArrayBuffer;
   derKey?: DerEncodedPublicKey;
 }
diff --git a/packages/agent/src/utils/buffer.ts b/packages/agent/src/utils/buffer.ts
index 6e339231..0792d0ce 100644
--- a/packages/agent/src/utils/buffer.ts
+++ b/packages/agent/src/utils/buffer.ts
@@ -20,7 +20,7 @@ export function toHex(buffer: ArrayBuffer): string {
   return [...new Uint8Array(buffer)].map(x => x.toString(16).padStart(2, '0')).join('');
 }
 
-const hexRe = new RegExp(/^([0-9A-F]{2})*$/i);
+const hexRe = new RegExp(/^[0-9a-fA-F]+$/);
 
 /**
  * Transforms a hexadecimal string into an array buffer.
diff --git a/packages/identity-secp256k1/src/buffer.ts b/packages/identity-secp256k1/src/buffer.ts
deleted file mode 100644
index 37366061..00000000
--- a/packages/identity-secp256k1/src/buffer.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-/**
- * Return an array buffer from its hexadecimal representation.
- * @param hexString The hexadecimal string.
- */
-export function fromHexString(hexString: string): ArrayBuffer {
-  return new Uint8Array((hexString.match(/.{1,2}/g) ?? []).map(byte => parseInt(byte, 16))).buffer;
-}
-
-/**
- * Returns an hexadecimal representation of an array buffer.
- * @param bytes The array buffer.
- */
-export function toHexString(bytes: ArrayBuffer): string {
-  return new Uint8Array(bytes).reduce((str, byte) => str + byte.toString(16).padStart(2, '0'), '');
-}
diff --git a/packages/identity-secp256k1/src/secp256k1.test.ts b/packages/identity-secp256k1/src/secp256k1.test.ts
index 86d47ac2..93b5d9d4 100644
--- a/packages/identity-secp256k1/src/secp256k1.test.ts
+++ b/packages/identity-secp256k1/src/secp256k1.test.ts
@@ -1,14 +1,9 @@
-import { DerEncodedPublicKey, PublicKey } from '@dfinity/agent';
-import { toHexString } from '@dfinity/candid/lib/cjs/utils/buffer';
+import { DerEncodedPublicKey, PublicKey, fromHex, toHex } from '@dfinity/agent';
 import { randomBytes } from 'crypto';
 import { sha256 } from '@noble/hashes/sha256';
 import { secp256k1 } from '@noble/curves/secp256k1';
 import { Secp256k1KeyIdentity, Secp256k1PublicKey } from './secp256k1';
 
-function fromHexString(hexString: string): ArrayBuffer {
-  return new Uint8Array((hexString.match(/.{1,2}/g) ?? []).map(byte => parseInt(byte, 16))).buffer;
-}
-
 // DER KEY SECP256K1 PREFIX = 3056301006072a8648ce3d020106052b8104000a03420004
 // These test vectors contain the hex encoding of the corresponding raw and DER versions
 // of secp256k1 keys that were generated using OpenSSL as follows:
@@ -40,7 +35,7 @@ const goldenSeed = '8caa0410fa5955c05d6877801806f627e5dd313957a59c70f8d8ef252a48
 describe('Secp256k1PublicKey Tests', () => {
   test('create from an existing public key', () => {
     testVectors.forEach(([rawPublicKeyHex]) => {
-      const publicKey: PublicKey = Secp256k1PublicKey.fromRaw(fromHexString(rawPublicKeyHex));
+      const publicKey: PublicKey = Secp256k1PublicKey.fromRaw(fromHex(rawPublicKeyHex));
 
       const newKey = Secp256k1PublicKey.from(publicKey);
       expect(newKey).toMatchSnapshot();
@@ -49,8 +44,8 @@ describe('Secp256k1PublicKey Tests', () => {
 
   test('DER encoding of SECP256K1 keys', async () => {
     testVectors.forEach(([rawPublicKeyHex, derEncodedPublicKeyHex]) => {
-      const publicKey = Secp256k1PublicKey.fromRaw(fromHexString(rawPublicKeyHex));
-      const expectedDerPublicKey = fromHexString(derEncodedPublicKeyHex);
+      const publicKey = Secp256k1PublicKey.fromRaw(fromHex(rawPublicKeyHex));
+      const expectedDerPublicKey = fromHex(derEncodedPublicKeyHex);
       expect(publicKey.toDer()).toEqual(expectedDerPublicKey);
     });
   });
@@ -59,7 +54,7 @@ describe('Secp256k1PublicKey Tests', () => {
     // Too short.
     expect(() => {
       Secp256k1PublicKey.fromDer(
-        fromHexString(
+        fromHex(
           '3056301006072a8648ce3d020106052b8104000a0342000401ec030acd7d1199f73ae3469329c114944e0693c89502f850bcc6bad397a5956767c79b410c29ac6f587eec84878020fdb54ba002a79b02aa153fe47b6',
         ) as DerEncodedPublicKey,
       );
@@ -67,7 +62,7 @@ describe('Secp256k1PublicKey Tests', () => {
     // Too long.
     expect(() => {
       Secp256k1PublicKey.fromDer(
-        fromHexString(
+        fromHex(
           '3056301006072a8648ce3d020106052b8104000a0342000401ec030acd7d1199f73ae3469329c114944e0693c89502f850bcc6bad397a5956767c79b410c29ac6f587eec84878020fdb54ba002a79b02aa153fe47b6ffd33' +
             '1b42211ce',
         ) as DerEncodedPublicKey,
@@ -77,7 +72,7 @@ describe('Secp256k1PublicKey Tests', () => {
     // Invalid DER-encoding.
     expect(() => {
       Secp256k1PublicKey.fromDer(
-        fromHexString(
+        fromHex(
           '0693c89502f850bcc6bad397a5956767c79b410c29ac6f54fdac09ea93a1b9b744b5f19f091ada7978ceb2f045875bca8ef9b75fa8061704e76de023c6a23d77a118c5c8d0f5efaf0dbbfcc3702d5590604717f639f6f00d',
         ) as DerEncodedPublicKey,
       );
@@ -131,11 +126,11 @@ describe('Secp256k1KeyIdentity Tests', () => {
   });
 
   test('generation from a seed should be supported', () => {
-    const seed = new Uint8Array(fromHexString(goldenSeed));
+    const seed = new Uint8Array(fromHex(goldenSeed));
     const identity = Secp256k1KeyIdentity.generate(seed);
     const publicKey = identity.getKeyPair().publicKey as Secp256k1PublicKey;
     publicKey.toRaw();
-    expect(toHexString(publicKey.toRaw())).toEqual(
+    expect(toHex(publicKey.toRaw())).toEqual(
       '04e2abe3b762fe0553f690d25f5100259b7eaeb3e476df6bd3dfc1d27e5dae56dad5a84f70bd87acc95ad54af0285f28c2be1e3b2f62a28a2fbad9fe44c84dc904',
     );
   });
@@ -195,7 +190,7 @@ describe('Secp256k1KeyIdentity Tests', () => {
   });
 });
 
-describe('public key serialization from', () => {
+describe('public key serialization from various types', () => {
   it('should serialize from an existing public key', () => {
     const baseKey = Secp256k1KeyIdentity.generate();
     const publicKey: PublicKey = baseKey.getPublicKey();
@@ -225,7 +220,7 @@ describe('public key serialization from', () => {
   });
   it('should serialize from a hex string', () => {
     const baseKey = Secp256k1KeyIdentity.generate();
-    const publicKey = toHexString(baseKey.getPublicKey().toRaw());
+    const publicKey = toHex(baseKey.getPublicKey().toRaw());
     const newKey = Secp256k1PublicKey.from(publicKey);
     expect(newKey).toBeDefined();
   });
@@ -235,6 +230,6 @@ describe('public key serialization from', () => {
     expect(shouldFail).toThrow('Cannot construct Secp256k1PublicKey from the provided key.');
 
     const shouldFailHex = () => Secp256k1PublicKey.from('not a hex string');
-    expect(shouldFailHex).toThrow('A Secp256k1 public key must be exactly 33 or 65 bytes long');
+    expect(shouldFailHex).toThrow('Invalid hexadecimal string');
   });
 });
diff --git a/packages/identity-secp256k1/src/secp256k1.ts b/packages/identity-secp256k1/src/secp256k1.ts
index 99f68bb4..55588555 100644
--- a/packages/identity-secp256k1/src/secp256k1.ts
+++ b/packages/identity-secp256k1/src/secp256k1.ts
@@ -5,6 +5,8 @@ import {
   Signature,
   uint8ToBuf,
   bufFromBufLike,
+  fromHex,
+  toHex,
 } from '@dfinity/agent';
 import { secp256k1 } from '@noble/curves/secp256k1';
 import { sha256 } from '@noble/hashes/sha256';
@@ -12,7 +14,6 @@ import { randomBytes } from '@noble/hashes/utils';
 import hdkey from 'hdkey';
 import { mnemonicToSeedSync } from 'bip39';
 import { PublicKey, SignIdentity } from '@dfinity/agent';
-import { fromHexString, toHexString } from './buffer';
 import { SECP256K1_OID, unwrapDER, wrapDER } from './der';
 
 declare type PublicKeyHex = string;
@@ -41,7 +42,7 @@ export class Secp256k1PublicKey implements PublicKey {
    */
   public static from(maybeKey: unknown): Secp256k1PublicKey {
     if (typeof maybeKey === 'string') {
-      const key = fromHexString(maybeKey);
+      const key = fromHex(maybeKey);
       return this.fromRaw(key);
     } else if (isObject(maybeKey)) {
       const key = maybeKey as KeyLike;
@@ -87,9 +88,6 @@ export class Secp256k1PublicKey implements PublicKey {
 
   // `fromRaw` and `fromDer` should be used for instantiation, not this constructor.
   private constructor(key: ArrayBuffer) {
-    if (key.byteLength !== 33 && key.byteLength !== 65) {
-      throw new Error('A Secp256k1 public key must be exactly 33 or 65 bytes long');
-    }
     this.#rawKey = bufFromBufLike(key);
     this.#derKey = Secp256k1PublicKey.derEncode(key);
   }
@@ -141,8 +139,8 @@ export class Secp256k1KeyIdentity extends SignIdentity {
   public static fromParsedJson(obj: JsonableSecp256k1Identity): Secp256k1KeyIdentity {
     const [publicKeyRaw, privateKeyRaw] = obj;
     return new Secp256k1KeyIdentity(
-      Secp256k1PublicKey.fromRaw(fromHexString(publicKeyRaw)),
-      fromHexString(privateKeyRaw),
+      Secp256k1PublicKey.fromRaw(fromHex(publicKeyRaw)),
+      fromHex(privateKeyRaw),
     );
   }
 
@@ -216,7 +214,7 @@ export class Secp256k1KeyIdentity extends SignIdentity {
    * @returns {JsonableSecp256k1Identity}
    */
   public toJSON(): JsonableSecp256k1Identity {
-    return [toHexString(this._publicKey.toRaw()), toHexString(this._privateKey)];
+    return [toHex(this._publicKey.toRaw()), toHex(this._privateKey)];
   }
 
   /**
@@ -232,9 +230,9 @@ export class Secp256k1KeyIdentity extends SignIdentity {
 
   /**
    * Return the public key.
-   * @returns {Secp256k1PublicKey}
+   * @returns {Required<PublicKey>}
    */
-  public getPublicKey(): Secp256k1PublicKey {
+  public getPublicKey(): Required<PublicKey> {
     return this._publicKey;
   }
 
diff --git a/packages/identity/src/identity/ed25519.test.ts b/packages/identity/src/identity/ed25519.test.ts
index 0b991927..22fd5d44 100644
--- a/packages/identity/src/identity/ed25519.test.ts
+++ b/packages/identity/src/identity/ed25519.test.ts
@@ -1,4 +1,4 @@
-import { DerEncodedPublicKey, fromHex } from '@dfinity/agent';
+import { DerEncodedPublicKey, PublicKey, fromHex, toHex } from '@dfinity/agent';
 import { Ed25519KeyIdentity, Ed25519PublicKey } from './ed25519';
 
 const testVectors: Array<[string, string]> = [
@@ -129,3 +129,47 @@ test('from JSON', async () => {
   const isValid = Ed25519KeyIdentity.verify(msg, signature, identity.getPublicKey().rawKey);
   expect(isValid).toBe(true);
 });
+
+describe('public key serialization from various types', () => {
+  it('should serialize from an existing public key', () => {
+    const baseKey = Ed25519KeyIdentity.generate();
+    const publicKey: PublicKey = baseKey.getPublicKey();
+    const newKey = Ed25519PublicKey.from(publicKey);
+    expect(newKey).toBeDefined();
+  });
+  it('should serialize from a raw key', () => {
+    const baseKey = Ed25519KeyIdentity.generate();
+    const publicKey = baseKey.getPublicKey().rawKey;
+    ArrayBuffer.isView(publicKey); //?
+    publicKey instanceof ArrayBuffer; //?
+
+    const newKey = Ed25519PublicKey.from(publicKey);
+    expect(newKey).toBeDefined();
+  });
+  it('should serialize from a DER key', () => {
+    const baseKey = Ed25519KeyIdentity.generate();
+    const publicKey = baseKey.getPublicKey().derKey;
+    const newKey = Ed25519PublicKey.from(publicKey);
+    expect(newKey).toBeDefined();
+  });
+  it('should serialize from a Uint8Array', () => {
+    const baseKey = Ed25519KeyIdentity.generate();
+    const publicKey = new Uint8Array(baseKey.getPublicKey().toRaw());
+    const newKey = Ed25519PublicKey.from(publicKey);
+    expect(newKey).toBeDefined();
+  });
+  it('should serialize from a hex string', () => {
+    const baseKey = Ed25519KeyIdentity.generate();
+    const publicKey = toHex(baseKey.getPublicKey().toRaw());
+    const newKey = Ed25519PublicKey.from(publicKey);
+    expect(newKey).toBeDefined();
+  });
+  it('should fail to parse an invalid key', () => {
+    const baseKey = 7;
+    const shouldFail = () => Ed25519PublicKey.from(baseKey as unknown);
+    expect(shouldFail).toThrow('Cannot construct Ed25519PublicKey from the provided key.');
+
+    const shouldFailHex = () => Ed25519PublicKey.from('not a hex string');
+    expect(shouldFailHex).toThrow('Invalid hexadecimal string');
+  });
+});
diff --git a/packages/identity/src/identity/ed25519.ts b/packages/identity/src/identity/ed25519.ts
index 3c36c563..c03e9aa1 100644
--- a/packages/identity/src/identity/ed25519.ts
+++ b/packages/identity/src/identity/ed25519.ts
@@ -10,12 +10,39 @@ import {
   wrapDER,
   fromHex,
   toHex,
+  bufFromBufLike,
 } from '@dfinity/agent';
 import { ed25519 } from '@noble/curves/ed25519';
 
+declare type KeyLike = PublicKey | DerEncodedPublicKey | ArrayBuffer | ArrayBufferView;
+
+function isObject(value: unknown) {
+  return value !== null && typeof value === 'object';
+}
+
 export class Ed25519PublicKey implements PublicKey {
-  public static from(key: PublicKey): Ed25519PublicKey {
-    return this.fromDer(key.toDer());
+  public static from(maybeKey: unknown): Ed25519PublicKey {
+    if (typeof maybeKey === 'string') {
+      const key = fromHex(maybeKey);
+      return this.fromRaw(key);
+    } else if (isObject(maybeKey)) {
+      const key = maybeKey as KeyLike;
+      if (isObject(key) && Object.hasOwnProperty.call(key, '__derEncodedPublicKey__')) {
+        return this.fromDer(key as DerEncodedPublicKey);
+      } else if (ArrayBuffer.isView(key)) {
+        const view = key as ArrayBufferView;
+        return this.fromRaw(bufFromBufLike(view.buffer));
+      } else if (key instanceof ArrayBuffer) {
+        return this.fromRaw(key);
+      } else if ('rawKey' in key) {
+        return this.fromRaw(key.rawKey as ArrayBuffer);
+      } else if ('derKey' in key) {
+        return this.fromDer(key.derKey as DerEncodedPublicKey);
+      } else if ('toDer' in key) {
+        return this.fromDer(key.toDer() as ArrayBuffer);
+      }
+    }
+    throw new Error('Cannot construct Ed25519PublicKey from the provided key.');
   }
 
   public static fromRaw(rawKey: ArrayBuffer): Ed25519PublicKey {
@@ -30,7 +57,9 @@ export class Ed25519PublicKey implements PublicKey {
   private static RAW_KEY_LENGTH = 32;
 
   private static derEncode(publicKey: ArrayBuffer): DerEncodedPublicKey {
-    return wrapDER(publicKey, ED25519_OID).buffer as DerEncodedPublicKey;
+    const key = wrapDER(publicKey, ED25519_OID).buffer as DerEncodedPublicKey;
+    key.__derEncodedPublicKey__ = undefined;
+    return key;
   }
 
   private static derDecode(key: DerEncodedPublicKey): ArrayBuffer {