diff --git a/src/encryption-types.ts b/src/encryption-types.ts
new file mode 100644
index 000000000..24cf9d3a4
--- /dev/null
+++ b/src/encryption-types.ts
@@ -0,0 +1,6 @@
+export type Eip1024EncryptedData = {
+  version: string;
+  nonce: string;
+  ephemPublicKey: string;
+  ciphertext: string;
+};
diff --git a/src/keyring.ts b/src/keyring.ts
new file mode 100644
index 000000000..d4859e650
--- /dev/null
+++ b/src/keyring.ts
@@ -0,0 +1,249 @@
+import type { Eip1024EncryptedData } from './encryption-types';
+import { Hex } from './hex';
+import { Json } from './json';
+import type { Transaction, SignedTransaction } from './transaction-types';
+
+/**
+ * A Keyring class.
+ *
+ * This type is used to validate the constructor signature and the `type`
+ * static property on Keyring classes. See the {@link Keyring} type for more
+ * information.
+ */
+export type KeyringClass<State extends Json> = {
+  /**
+   * The Keyring constructor. Takes a single parameter, an "options" object.
+   * See the documentation for the specific keyring for more information about
+   * what these options are.
+   *
+   * @param options - The constructor options. Differs between keyring
+   * implementations.
+   */
+  new (options?: Record<string, unknown>): Keyring<State>;
+
+  /**
+   * The name of this type of keyring. This must uniquely identify the
+   * keyring type.
+   */
+  type: string;
+};
+
+/**
+ * A keyring is something that can sign messages. Keyrings are used to add new
+ * signing strategies; each strategy is a new keyring.
+ *
+ * Each keyring manages a collection of key pairs, which we call "accounts".
+ * Each account is referred to by its "address", which is a unique identifier
+ * derived from the public key. The address is always a "0x"-prefixed
+ * hexidecimal string.
+ *
+ * The keyring might store the private key for each account as well, but it's
+ * not guaranteed. Some keyrings delegate signing, so they don't need the
+ * private key directly. The keyring (and in particular the keyring state)
+ * should be treated with care though, just in case it does contain sensitive
+ * material such as a private key.
+ */
+export type Keyring<State extends Json> = {
+  /**
+   * The name of this type of keyring. This must match the `type` property of
+   * the keyring class.
+   */
+  type: string;
+
+  /**
+   * Get the addresses for all accounts in this keyring.
+   *
+   * @returns A list of the account addresses for this keyring
+   */
+  getAccounts(): Promise<Hex[]>;
+
+  /**
+   * Add an account to the keyring.
+   *
+   * @param number - The number of accounts to add. Usually defaults to 1.
+   * @returns A list of the newly added account addresses.
+   */
+  addAccounts(number: number): Promise<Hex[]>;
+
+  /**
+   * Serialize the keyring state as a JSON-serializable object.
+   *
+   * @returns A JSON-serializable representation of the keyring state.
+   */
+  serialize(): Promise<State>;
+
+  /**
+   * Deserialize the given keyring state, overwriting any existing state with
+   * the serialized state provided.
+   *
+   * @param state - A JSON-serializable representation of the keyring state.
+   */
+  deserialize(state: State): Promise<void>;
+
+  /**
+   * Remove an account from the keyring.
+   *
+   * @param address - The address of the account to remove.
+   */
+  removeAccount?(address: Hex): void;
+
+  /**
+   * Export the private key for one of the keyring accounts.
+   *
+   * Some keyrings accept an "options" parameter as well. See the documentation
+   * for the specific keyring for more information about what these options
+   * are. For some keyrings, the options parameter is used to allow exporting a
+   * private key that is derived from the given account, rather than exporting
+   * that account's private key directly.
+   *
+   * @param address - The address of the account to export.
+   * @param options - Export options; differs between keyrings.
+   * @returns The non-prefixed, hex-encoded private key that was requested.
+   */
+  exportAccount?(
+    address: Hex,
+    options?: Record<string, unknown>,
+  ): Promise<string>;
+
+  /**
+   * Get the "app key" address for the given account and origin. An app key is
+   * an application-specific key pair. See {@link https://eips.ethereum.org/EIPS/eip-1775|EIP-1775}
+   * for more information. The {@link https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Origin|origin}
+   * is used as the unique identifier for the application, and it's used as
+   * part of the key derivation process.
+   *
+   * @param address - The address of the account the app key is derived from.
+   * @param origin - The origin of the application.
+   * @returns The address of the app key for the given account and origin.
+   */
+  getAppKeyAddress?(address: Hex, origin: string): Promise<Hex>;
+
+  /**
+   * Sign a transaction. This is equivalent to the `eth_signTransaction`
+   * Ethereum JSON-RPC method. See the Ethereum JSON-RPC API documentation for
+   * more details.
+   *
+   * Some keyrings accept an "options" parameter as well. See the documentation
+   * for the specific keyring for more information about what these options
+   * are. For some keyrings, the options parameter can even change which key is
+   * used for signing (e.g. signing with app keys).
+   *
+   * @param address - The address of the account to use for signing.
+   * @param transaction - The transaction to sign.
+   * @param options - Signing options; differs between keyrings.
+   * @returns The signed transaction.
+   */
+  signTransaction?(
+    address: Hex,
+    transaction: Transaction,
+    options?: Record<string, unknown>,
+  ): Promise<SignedTransaction>;
+
+  /**
+   * Sign a message. This is equivalent to an older version of the the
+   * `eth_sign` Ethereum JSON-RPC method. The message is signed using ECDSA,
+   * using the curve secp256k1 the Keccak-256 hash function.
+   *
+   * For more information about this method and why we still support it, see
+   * the {@link https://docs.metamask.io/guide/signing-data.html|MetaMask Docs}.
+   *
+   * Some keyrings accept an "options" parameter as well. See the documentation
+   * for the specific keyring for more information about what these options
+   * are. For some keyrings, the options parameter can even change which key is
+   * used for signing (e.g. signing with app keys).
+   *
+   * @param address - The address of the account to use for signing.
+   * @param message - The message to sign.
+   * @param options - Signing options; differs between keyrings.
+   * @returns The signed message.
+   */
+  signMessage?(
+    address: Hex,
+    message: string,
+    options?: Record<string, unknown>,
+  ): Promise<string>;
+
+  /**
+   * Sign a message. This is equivalent to the `eth_sign` Ethereum JSON-RPC
+   * method, which is exposed by MetaMask as the method `personal_sign`. See
+   * the Ethereum JSON-RPC API documentation for more details.
+   *
+   * For more information about this method and why we call it `personal_sign`,
+   * see the {@link https://docs.metamask.io/guide/signing-data.html|MetaMask Docs}.
+   *
+   * Some keyrings accept an "options" parameter as well. See the documentation
+   * for the specific keyring for more information about what these options
+   * are. For some keyrings, the options parameter can even change which key is
+   * used for signing (e.g. signing with app keys).
+   *
+   * @param address - The address of the account to use for signing.
+   * @param message - The message to sign.
+   * @param options - Signing options; differs between keyrings.
+   * @returns The signed message.
+   */
+  signPersonalMessage?(
+    address: Hex,
+    message: Hex,
+    options?: { version?: string } & Record<string, unknown>,
+  ): Promise<string>;
+
+  /**
+   * Sign a message. This is equivalent to the `eth_signTypedData` Ethereum
+   * JSON-RPC method. See {@link https://github.com/ethereum/EIPs/blob/master/EIPS/eip-712.md|EIP-712}
+   * for more details.
+   *
+   * The "version" option dictates which version of `eth_signTypedData` is
+   * used. The latest version reflects the specification most closely, whereas
+   * earlier versions reflect earlier drafts of the specification that are
+   * still supported for backwards-compatibility reasons. For more information
+   * about why we support multiple versions, see the {@link https://docs.metamask.io/guide/signing-data.html|MetaMask Docs}.
+   *
+   * Some keyrings accept additional options as well. See the documentation for
+   * the specific keyring for more information about what these options are.
+   * For some keyrings, the options parameter can even change which key is used
+   * for signing (e.g. signing with app keys).
+   *
+   * @param address - The address of the account to use for signing.
+   * @param typedData - The data to sign.
+   * @param options - Signing options; differs between keyrings.
+   * @returns The signed message.
+   */
+  signTypedData?(
+    address: Hex,
+    typedData: Record<string, unknown>,
+    options?: Record<string, unknown>,
+  ): Promise<string>;
+
+  /**
+   * Get a public key to use for encryption. This is equivalent to the
+   * ` eth_getEncryptionPublicKey` JSON-RPC method. See the {@link https://docs.metamask.io/guide/rpc-api.html#eth-getencryptionpublickey|MetaMask Docs}
+   * for more information.
+   *
+   * Some keyrings accept an "options" parameter as well. See the documentation
+   * for the specific keyring for more information about what these options
+   * are. For some keyrings, the options parameter can even change which key is
+   * used (e.g. encrypting with app keys).
+   *
+   * @param account - The address of the account you want the encryption key for.
+   * @param options - Options; differs between keyrings.
+   */
+  getEncryptionPublicKey?(
+    account: Hex,
+    options?: Record<string, unknown>,
+  ): Promise<string>;
+
+  /**
+   * Decrypt an encrypted message. This is equivalent to the `  eth_decrypt`
+   * JSON-RPC method. See the {@link https://docs.metamask.io/guide/rpc-api.html#eth-decrypt|MetaMask Docs}
+   * for more information.
+   *
+   * @param account - The address of the account you want to use to decrypt
+   * the message.
+   * @param encryptedData - The encrypted data that you want to decrypt.
+   * @returns The decrypted data.
+   */
+  decryptMessage?(
+    account: Hex,
+    encryptedData: Eip1024EncryptedData,
+  ): Promise<string>;
+};
diff --git a/src/transaction-types.ts b/src/transaction-types.ts
new file mode 100644
index 000000000..691d6b321
--- /dev/null
+++ b/src/transaction-types.ts
@@ -0,0 +1,134 @@
+import { Bytes } from './bytes';
+import { Hex } from './hex';
+
+export type Transaction =
+  | LegacyTransaction
+  | EIP2930Transaction
+  | EIP1559Transaction;
+
+export type SignedTransaction = Transaction & Signature;
+
+export type Signature = {
+  /**
+   * EC signature parameter
+   * 32 bytes long sequence.
+   */
+  r: Bytes;
+
+  /**
+   * EC signature parameter
+   * Signature proof.
+   * 32 bytes long sequence
+   */
+  s: Bytes;
+
+  /**
+   * Recovery identifier. It can be either 0x1b or 0x1c
+   * 1 byte long sequence
+   */
+  yParity: Bytes;
+};
+
+/**
+ * Base Ethereum Transaction
+ */
+export type BaseTransaction = {
+  /**
+   * Sequentially incrementing counter which indicates the transaction
+   * number from the account
+   */
+  nonce: Bytes;
+
+  /**
+   * The address of the sender, that will be signing the transaction
+   */
+  from: Hex | Uint8Array;
+
+  /**
+   * The receiving address.
+   * If an externally-owned account, the transaction will transfer value.
+   * If a contract account, the transaction will execute the contract code.
+   */
+  to: Hex | Uint8Array;
+
+  /**
+   * The amount of Ether sent.
+   */
+  value: Bytes;
+
+  /**
+   * Maximum amount of gas units that this transaction can consume.
+   */
+  gasLimit: Bytes;
+
+  /**
+   * Arbitrary data.
+   */
+  data?: Bytes;
+};
+
+/**
+ * Typed Ethereum Transaction
+ */
+export type TypedTransaction = BaseTransaction & {
+  /**
+   * Transaction type.
+   */
+  type: number;
+};
+
+/**
+ * Ethereum Legacy Transaction
+ * Reference: https://ethereum.org/en/developers/docs/transactions/
+ */
+export type LegacyTransaction = BaseTransaction & {
+  /**
+   * Transaction's gas price.
+   */
+  gasPrice: Bytes | null;
+};
+
+/**
+ * EIP-2930 Transaction: Optional Access Lists
+ * Reference: https://eips.ethereum.org/EIPS/eip-2930
+ */
+export type EIP2930Transaction = TypedTransaction & {
+  /**
+   * Transaction type.
+   */
+  type: 1;
+
+  /**
+   * Transaction chain ID
+   */
+  chainId: Bytes;
+
+  /**
+   * List of addresses and storage keys that the transaction plans to access
+   */
+  accessList:
+    | { address: Hex; storageKeys: Hex[] }[]
+    | { address: Uint8Array; storageKeys: Uint8Array[] }[];
+};
+
+/**
+ * EIP-1559 Transaction: Fee market change for ETH 1.0 chain (Type-2)
+ *
+ * Reference: https://eips.ethereum.org/EIPS/eip-1559
+ */
+export type EIP1559Transaction = TypedTransaction & {
+  /**
+   * Transaction type.
+   */
+  type: 2;
+
+  /**
+   * Maximum fee to give to the miner
+   */
+  maxPriorityFeePerGas: Bytes;
+
+  /**
+   * Maximum total fee
+   */
+  maxFeePerGas: Bytes;
+};