diff --git a/web3.js/examples/account.js b/web3.js/examples/account.js
index ca52858315..707bf13c83 100644
--- a/web3.js/examples/account.js
+++ b/web3.js/examples/account.js
@@ -7,4 +7,4 @@ const solanaWeb3 = require('..');
 //const solanaWeb3 = require('@solana/web3.js');
 
 const account = new solanaWeb3.Account();
-console.log(account.publicKey);
+console.log(account.publicKey.toString());
diff --git a/web3.js/flow-typed/bn.js.js b/web3.js/flow-typed/bn.js.js
new file mode 100644
index 0000000000..5412142593
--- /dev/null
+++ b/web3.js/flow-typed/bn.js.js
@@ -0,0 +1,4 @@
+declare module 'bn.js' {
+  // TODO: Fill in types
+  declare module.exports: any;
+}
diff --git a/web3.js/module.flow.js b/web3.js/module.flow.js
index 921c002653..25397b9749 100644
--- a/web3.js/module.flow.js
+++ b/web3.js/module.flow.js
@@ -13,11 +13,20 @@
 declare module '@solana/web3.js' {
   declare export type PublicKey = string;
 
+  // === src/publickey.js ===
+  declare export class PublicKey {
+    constructor(number: string | Buffer | Array<number>): PublicKey;
+    static isPublicKey(o: Object): boolean;
+    equals(publickey: PublicKey): boolean;
+    toBase58(): string;
+    toBuffer(): Buffer;
+  }
+
   // === src/account.js ===
   declare export class Account {
     constructor(secretKey: ?Buffer): Account;
     publicKey: PublicKey;
-    secretKey: PublicKey;
+    secretKey: Buffer;
   }
 
   // === src/budget-program.js ===
@@ -84,6 +93,5 @@ declare module '@solana/web3.js' {
     constructor(opts?: TransactionCtorFields): Transaction;
     sign(from: Account): void;
     serialize(): Buffer;
-    static serializePublicKey(key: PublicKey): Buffer;
   }
 }
diff --git a/web3.js/package-lock.json b/web3.js/package-lock.json
index afd4e3f82a..6ad1cf257b 100644
--- a/web3.js/package-lock.json
+++ b/web3.js/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "@solana/web3.js",
-  "version": "0.0.7",
+  "version": "0.0.0-development",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -2261,8 +2261,7 @@
     "bn.js": {
       "version": "4.11.8",
       "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-4.11.8.tgz",
-      "integrity": "sha512-ItfYfPLkWHUjckQCk8xC+LwxgK8NYcXywGigJgSwOP8Y2iyWT4f2vsZnoOXTTbo+o5yXmIUJ4gn5538SO5S3gA==",
-      "dev": true
+      "integrity": "sha512-ItfYfPLkWHUjckQCk8xC+LwxgK8NYcXywGigJgSwOP8Y2iyWT4f2vsZnoOXTTbo+o5yXmIUJ4gn5538SO5S3gA=="
     },
     "boolbase": {
       "version": "1.0.0",
diff --git a/web3.js/package.json b/web3.js/package.json
index 2667f6e63b..c7d422dc0a 100644
--- a/web3.js/package.json
+++ b/web3.js/package.json
@@ -43,6 +43,7 @@
   },
   "dependencies": {
     "babel-runtime": "^6.26.0",
+    "bn.js": "^4.11.8",
     "bs58": "^4.0.1",
     "jayson": "^2.0.6",
     "node-fetch": "^2.2.0",
diff --git a/web3.js/src/account.js b/web3.js/src/account.js
index 1f2a8a4e87..d9405a8ff3 100644
--- a/web3.js/src/account.js
+++ b/web3.js/src/account.js
@@ -1,14 +1,8 @@
 // @flow
 import nacl from 'tweetnacl';
-import bs58 from 'bs58';
 import type {KeyPair} from 'tweetnacl';
 
-/**
- * Base 58 encoded public key
- *
- * @typedef {string} PublicKey
- */
-export type PublicKey = string;
+import {PublicKey} from './publickey';
 
 /**
  * An account key pair (public and secret keys).
@@ -36,7 +30,7 @@ export class Account {
    * The public key for this account
    */
   get publicKey(): PublicKey {
-    return bs58.encode(this._keypair.publicKey);
+    return new PublicKey(this._keypair.publicKey);
   }
 
   /**
diff --git a/web3.js/src/budget-program.js b/web3.js/src/budget-program.js
index 742e677068..4a4707de9e 100644
--- a/web3.js/src/budget-program.js
+++ b/web3.js/src/budget-program.js
@@ -1,7 +1,7 @@
 // @flow
 
 import {Transaction} from './transaction';
-import type {PublicKey} from './account';
+import {PublicKey} from './publickey';
 
 /**
  * Represents a condition that is met by executing a `applySignature()`
@@ -54,7 +54,7 @@ export type BudgetCondition = SignatureCondition | TimestampCondition;
  * @private
  */
 function serializePayment(payment: Payment): Buffer {
-  const toData = Transaction.serializePublicKey(payment.to);
+  const toData = payment.to.toBuffer();
   const userdata = Buffer.alloc(8 + toData.length);
   userdata.writeUInt32LE(payment.amount, 0);
   toData.copy(userdata, 8);
@@ -98,7 +98,7 @@ function serializeCondition(condition: BudgetCondition) {
   case 'timestamp':
   {
     const date = serializeDate(condition.when);
-    const from = Transaction.serializePublicKey(condition.from);
+    const from = condition.from.toBuffer();
 
     const userdata = Buffer.alloc(4 + date.length + from.length);
     userdata.writeUInt32LE(0, 0); // Condition enum = Timestamp
@@ -108,7 +108,7 @@ function serializeCondition(condition: BudgetCondition) {
   }
   case 'signature':
   {
-    const from = Transaction.serializePublicKey(condition.from);
+    const from = condition.from.toBuffer();
 
     const userdata = Buffer.alloc(4 + from.length);
     userdata.writeUInt32LE(1, 0); // Condition enum = Signature
@@ -130,7 +130,7 @@ export class BudgetProgram {
    * Public key that identifies the Budget program
    */
   static get programId(): PublicKey {
-    return '4uQeVj5tqViQh7yWWGStvkEG1Zmhx6uasJtWCJziofM';
+    return new PublicKey('0x100000000000000000000000000000000000000000000000000000000000000');
   }
 
   /**
diff --git a/web3.js/src/connection.js b/web3.js/src/connection.js
index fd4bef99eb..af8cf21e3c 100644
--- a/web3.js/src/connection.js
+++ b/web3.js/src/connection.js
@@ -4,10 +4,10 @@ import assert from 'assert';
 import fetch from 'node-fetch';
 import jayson from 'jayson/lib/client/browser';
 import {struct} from 'superstruct';
-import bs58 from 'bs58';
 
 import {Transaction} from './transaction';
-import type {Account, PublicKey} from './account';
+import {PublicKey} from './publickey';
+import type {Account} from './account';
 import type {TransactionSignature, TransactionId} from './transaction';
 
 type RpcRequest = (methodName: string, args: Array<any>) => any;
@@ -174,7 +174,7 @@ export class Connection {
   async getBalance(publicKey: PublicKey): Promise<number> {
     const unsafeRes = await this._rpcRequest(
       'getBalance',
-      [publicKey]
+      [publicKey.toBase58()]
     );
     const res = GetBalanceRpcResult(unsafeRes);
     if (res.error) {
@@ -190,7 +190,7 @@ export class Connection {
   async getAccountInfo(publicKey: PublicKey): Promise<AccountInfo> {
     const unsafeRes = await this._rpcRequest(
       'getAccountInfo',
-      [publicKey]
+      [publicKey.toBase58()]
     );
     const res = GetAccountInfoRpcResult(unsafeRes);
     if (res.error) {
@@ -202,7 +202,7 @@ export class Connection {
 
     return {
       tokens: result.tokens,
-      programId: bs58.encode(result.program_id),
+      programId: new PublicKey(result.program_id),
       userdata: Buffer.from(result.userdata),
     };
   }
@@ -280,7 +280,7 @@ export class Connection {
    * Request an allocation of tokens to the specified account
    */
   async requestAirdrop(to: PublicKey, amount: number): Promise<TransactionSignature> {
-    const unsafeRes = await this._rpcRequest('requestAirdrop', [to, amount]);
+    const unsafeRes = await this._rpcRequest('requestAirdrop', [to.toBase58(), amount]);
     const res = RequestAirdropRpcResult(unsafeRes);
     if (res.error) {
       throw new Error(res.error.message);
diff --git a/web3.js/src/index.js b/web3.js/src/index.js
index f613a2d68d..506a72cc38 100644
--- a/web3.js/src/index.js
+++ b/web3.js/src/index.js
@@ -1,6 +1,7 @@
 // @flow
 export {Account} from './account';
-export {Connection} from './connection';
-export {Transaction} from './transaction';
-export {SystemProgram} from './system-program';
 export {BudgetProgram} from './budget-program';
+export {Connection} from './connection';
+export {PublicKey} from './publickey';
+export {SystemProgram} from './system-program';
+export {Transaction} from './transaction';
diff --git a/web3.js/src/publickey.js b/web3.js/src/publickey.js
new file mode 100644
index 0000000000..9af5f9c499
--- /dev/null
+++ b/web3.js/src/publickey.js
@@ -0,0 +1,70 @@
+// @flow
+
+import BN from 'bn.js';
+import bs58 from 'bs58';
+
+/**
+ * A public key
+ */
+export class PublicKey {
+  _bn: BN;
+
+  /**
+   * Create a new PublicKey object
+   */
+  constructor(number: string | Buffer | Array<number>) {
+    let radix = 10;
+
+    if (typeof number === 'string' && number.startsWith('0x')) {
+      this._bn = new BN(number.substring(2), 16);
+    } else {
+      this._bn = new BN(number, radix);
+    }
+    if (this._bn.byteLength() > 32) {
+      throw new Error(`Invalid public key input`);
+    }
+  }
+
+  /**
+   * Checks if the provided object is a PublicKey
+   */
+  static isPublicKey(o: Object): boolean {
+    return o instanceof PublicKey;
+  }
+
+  /**
+   * Checks if two publicKeys are equal
+   */
+  equals(publicKey: PublicKey): boolean {
+    return this._bn.eq(publicKey._bn);
+  }
+
+  /**
+   * Return the base-58 representation of the public key
+   */
+  toBase58(): string {
+    return bs58.encode(this.toBuffer());
+  }
+
+  /**
+   * Return the base-58 representation of the public key
+   */
+  toBuffer(): Buffer {
+    const b = this._bn.toBuffer();
+    if (b.length === 32) {
+      return b;
+    }
+
+    const zeroPad = new Buffer(32);
+    b.copy(zeroPad, 32 - b.length);
+    return zeroPad;
+  }
+
+  /**
+   * Returns a string representation of the public key
+   */
+  toString(): string {
+    return this.toBase58();
+  }
+}
+
diff --git a/web3.js/src/system-program.js b/web3.js/src/system-program.js
index 2804b7f036..8029e83009 100644
--- a/web3.js/src/system-program.js
+++ b/web3.js/src/system-program.js
@@ -3,7 +3,7 @@
 import assert from 'assert';
 
 import {Transaction} from './transaction';
-import type {PublicKey} from './account';
+import {PublicKey} from './publickey';
 
 /**
  * Factory class for transactions to interact with the System program
@@ -13,7 +13,7 @@ export class SystemProgram {
    * Public key that identifies the System program
    */
   static get programId(): PublicKey {
-    return '11111111111111111111111111111111';
+    return new PublicKey('0x000000000000000000000000000000000000000000000000000000000000000');
   }
 
   /**
@@ -38,7 +38,7 @@ export class SystemProgram {
     userdata.writeUInt32LE(space, pos); // space as u64
     pos += 8;
 
-    const programIdBytes = Transaction.serializePublicKey(programId);
+    const programIdBytes = programId.toBuffer();
     programIdBytes.copy(userdata, pos);
     pos += 32;
 
@@ -84,7 +84,7 @@ export class SystemProgram {
     userdata.writeUInt32LE(1, pos); // Assign instruction
     pos += 4;
 
-    const programIdBytes = Transaction.serializePublicKey(programId);
+    const programIdBytes = programId.toBuffer();
     programIdBytes.copy(userdata, pos);
     pos += programIdBytes.length;
 
diff --git a/web3.js/src/transaction.js b/web3.js/src/transaction.js
index 23fc39080b..8aec617998 100644
--- a/web3.js/src/transaction.js
+++ b/web3.js/src/transaction.js
@@ -4,7 +4,8 @@ import assert from 'assert';
 import nacl from 'tweetnacl';
 import bs58 from 'bs58';
 
-import type {Account, PublicKey} from './account';
+import type {Account} from './account';
+import type {PublicKey} from './publickey';
 
 /**
  * @typedef {string} TransactionSignature
@@ -92,14 +93,14 @@ export class Transaction {
     transactionData.writeUInt32LE(this.keys.length, pos);  // u64
     pos += 8;
     for (let key of this.keys) {
-      const keyBytes = Transaction.serializePublicKey(key);
+      const keyBytes = key.toBuffer();
       keyBytes.copy(transactionData, pos);
       pos += 32;
     }
 
     // serialize `this.programId`
     if (this.programId) {
-      const keyBytes = Transaction.serializePublicKey(this.programId);
+      const keyBytes = this.programId.toBuffer();
       keyBytes.copy(transactionData, pos);
     }
     pos += 32;
@@ -158,14 +159,5 @@ export class Transaction {
     transactionData.copy(wireTransaction, signature.length);
     return wireTransaction;
   }
-
-  /**
-   * Serializes a public key into the wire format
-   */
-  static serializePublicKey(key: PublicKey): Buffer {
-    const data = Buffer.from(bs58.decode(key));
-    assert(data.length === 32);
-    return data;
-  }
 }
 
diff --git a/web3.js/test/account.test.js b/web3.js/test/account.test.js
index 8c18317081..341c085f79 100644
--- a/web3.js/test/account.test.js
+++ b/web3.js/test/account.test.js
@@ -1,10 +1,10 @@
 // @flow
 import {Account} from '../src/account';
+import {PublicKey} from '../src/publickey';
 
 test('generate new account', () => {
   const account = new Account();
-  expect(account.publicKey.length).toBeGreaterThanOrEqual(43);
-  expect(account.publicKey.length).toBeLessThanOrEqual(44);
+  expect(PublicKey.isPublicKey(account.publicKey)).toBeTruthy();
   expect(account.secretKey).toHaveLength(64);
 });
 
@@ -17,5 +17,5 @@ test('account from secret key', () => {
     74, 101, 217, 139, 135, 139, 153, 34
   ]);
   const account = new Account(secretKey);
-  expect(account.publicKey).toBe('2q7pyhPwAwZ3QMfZrnAbDhnh9mDUqycszcpf86VgQxhF');
+  expect(account.publicKey.toBase58()).toBe('2q7pyhPwAwZ3QMfZrnAbDhnh9mDUqycszcpf86VgQxhF');
 });
diff --git a/web3.js/test/connection.test.js b/web3.js/test/connection.test.js
index 8389159e81..4cc20f373a 100644
--- a/web3.js/test/connection.test.js
+++ b/web3.js/test/connection.test.js
@@ -26,7 +26,7 @@ test('get account info - error', () => {
     url,
     {
       method: 'getAccountInfo',
-      params: [account.publicKey],
+      params: [account.publicKey.toBase58()],
     },
     errorResponse,
   ]);
@@ -44,7 +44,7 @@ test('get balance', async () => {
     url,
     {
       method: 'getBalance',
-      params: [account.publicKey],
+      params: [account.publicKey.toBase58()],
     },
     {
       error: null,
@@ -56,23 +56,6 @@ test('get balance', async () => {
   expect(balance).toBeGreaterThanOrEqual(0);
 });
 
-test('get balance - error', () => {
-  const connection = new Connection(url);
-
-  const invalidPublicKey = 'not a public key';
-  mockRpc.push([
-    url,
-    {
-      method: 'getBalance',
-      params: [invalidPublicKey],
-    },
-    errorResponse,
-  ]);
-
-  expect(connection.getBalance(invalidPublicKey))
-  .rejects.toThrow(errorMessage);
-});
-
 test('confirm transaction - error', () => {
   const connection = new Connection(url);
 
@@ -174,7 +157,7 @@ test('request airdrop', async () => {
     url,
     {
       method: 'requestAirdrop',
-      params: [account.publicKey, 40],
+      params: [account.publicKey.toBase58(), 40],
     },
     {
       error: null,
@@ -185,7 +168,7 @@ test('request airdrop', async () => {
     url,
     {
       method: 'requestAirdrop',
-      params: [account.publicKey, 2],
+      params: [account.publicKey.toBase58(), 2],
     },
     {
       error: null,
@@ -196,7 +179,7 @@ test('request airdrop', async () => {
     url,
     {
       method: 'getBalance',
-      params: [account.publicKey],
+      params: [account.publicKey.toBase58()],
     },
     {
       error: null,
@@ -214,7 +197,7 @@ test('request airdrop', async () => {
     url,
     {
       method: 'getAccountInfo',
-      params: [account.publicKey],
+      params: [account.publicKey.toBase58()],
     },
     {
       error: null,
@@ -226,31 +209,13 @@ test('request airdrop', async () => {
         tokens: 42,
         userdata: [],
       }
-
     }
   ]);
 
   const accountInfo = await connection.getAccountInfo(account.publicKey);
   expect(accountInfo.tokens).toBe(42);
   expect(accountInfo.userdata).toHaveLength(0);
-  expect(accountInfo.programId).toBe(SystemProgram.programId);
-});
-
-test('request airdrop - error', () => {
-  const invalidPublicKey = 'not a public key';
-  const connection = new Connection(url);
-
-  mockRpc.push([
-    url,
-    {
-      method: 'requestAirdrop',
-      params: [invalidPublicKey, 1],
-    },
-    errorResponse
-  ]);
-
-  expect(connection.requestAirdrop(invalidPublicKey, 1))
-  .rejects.toThrow(errorMessage);
+  expect(accountInfo.programId).toEqual(SystemProgram.programId);
 });
 
 test('transaction', async () => {
@@ -262,7 +227,7 @@ test('transaction', async () => {
     url,
     {
       method: 'requestAirdrop',
-      params: [accountFrom.publicKey, 12],
+      params: [accountFrom.publicKey.toBase58(), 12],
     },
     {
       error: null,
@@ -273,7 +238,7 @@ test('transaction', async () => {
     url,
     {
       method: 'getBalance',
-      params: [accountFrom.publicKey],
+      params: [accountFrom.publicKey.toBase58()],
     },
     {
       error: null,
@@ -287,7 +252,7 @@ test('transaction', async () => {
     url,
     {
       method: 'requestAirdrop',
-      params: [accountTo.publicKey, 21],
+      params: [accountTo.publicKey.toBase58(), 21],
     },
     {
       error: null,
@@ -298,7 +263,7 @@ test('transaction', async () => {
     url,
     {
       method: 'getBalance',
-      params: [accountTo.publicKey],
+      params: [accountTo.publicKey.toBase58()],
     },
     {
       error: null,
@@ -375,7 +340,7 @@ test('transaction', async () => {
     url,
     {
       method: 'getBalance',
-      params: [accountFrom.publicKey],
+      params: [accountFrom.publicKey.toBase58()],
     },
     {
       error: null,
@@ -388,7 +353,7 @@ test('transaction', async () => {
     url,
     {
       method: 'getBalance',
-      params: [accountTo.publicKey],
+      params: [accountTo.publicKey.toBase58()],
     },
     {
       error: null,
diff --git a/web3.js/test/publickey.test.js b/web3.js/test/publickey.test.js
new file mode 100644
index 0000000000..dd1d5f7732
--- /dev/null
+++ b/web3.js/test/publickey.test.js
@@ -0,0 +1,51 @@
+// @flow
+import {PublicKey} from '../src/publickey';
+
+test('invalid', () => {
+  expect(() => {
+    new PublicKey([
+      3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+    ]);
+  }).toThrow();
+
+  expect(() => {
+    new PublicKey('0x300000000000000000000000000000000000000000000000000000000000000000000');
+  }).toThrow();
+
+  expect(() => {
+    new PublicKey('135693854574979916511997248057056142015550763280047535983739356259273198796800000');
+  }).toThrow();
+});
+
+test('equals', () => {
+  const arrayKey = new PublicKey([
+    3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  ]);
+  const hexKey = new PublicKey('0x300000000000000000000000000000000000000000000000000000000000000');
+  const decimalKey = new PublicKey('1356938545749799165119972480570561420155507632800475359837393562592731987968');
+
+  expect(arrayKey.equals(hexKey)).toBeTruthy();
+  expect(arrayKey.equals(decimalKey)).toBeTruthy();
+});
+
+test('isPublicKey', () => {
+  const key = new PublicKey('0x100000000000000000000000000000000000000000000000000000000000000');
+  expect(PublicKey.isPublicKey(key)).toBeTruthy();
+  expect(PublicKey.isPublicKey({})).toBeFalsy();
+});
+
+test('toBase58', () => {
+  const key = new PublicKey('0x300000000000000000000000000000000000000000000000000000000000000');
+  expect(key.toBase58()).toBe('CiDwVBFgWV9E5MvXWoLgnEgn2hK7rJikbvfWavzAQz3');
+});
+
+test('toBuffer', () => {
+  const key = new PublicKey('0x300000000000000000000000000000000000000000000000000000000000000');
+  expect(key.toBuffer()).toHaveLength(32);
+  expect(key.toBase58()).toBe('CiDwVBFgWV9E5MvXWoLgnEgn2hK7rJikbvfWavzAQz3');
+
+  const key2 = new PublicKey('0x000000000000000000000000000000000000000000000000000000000000000');
+  expect(key2.toBuffer()).toHaveLength(32);
+  expect(key2.toBase58()).toBe('11111111111111111111111111111111');
+});
+