diff --git a/README.md b/README.md
index c94389e..9d85a9f 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 ## Testing
 
 ```sh
-wget -qO- https://cache.agilebits.com/security-kb/freddy-2013-12-04.tar.gz | tar xvz -
+wget -qO- https://cache.agilebits.com/security-kb/freddy-2013-12-04.tar.gz | tar xvz
 mv onepassword_data freddy-2013-12-04.opvault
 pnpm run test
 ```
diff --git a/src/errors.ts b/src/errors.ts
new file mode 100644
index 0000000..21f0919
--- /dev/null
+++ b/src/errors.ts
@@ -0,0 +1,11 @@
+export abstract class OPVaultError extends Error {}
+
+export class AssertionError extends OPVaultError {}
+
+export class HMACAssertionError extends AssertionError {}
+
+export function invariant(condition: any, message?: string): asserts condition {
+  if (!condition) {
+    throw new AssertionError(message)
+  }
+}
diff --git a/src/models.ts b/src/models.ts
index b9c89b6..3f32d95 100644
--- a/src/models.ts
+++ b/src/models.ts
@@ -1,4 +1,4 @@
-import invariant from "tiny-invariant"
+import { invariant } from "./errors"
 
 export enum Category {
   Login = 1,
diff --git a/src/vault.ts b/src/vault.ts
index accd3ae..f1358a1 100644
--- a/src/vault.ts
+++ b/src/vault.ts
@@ -1,4 +1,5 @@
 import * as crypto from "crypto"
+import { HMACAssertionError, invariant } from "./errors"
 import type { IFileSystem } from "./fs"
 import { OnePasswordFileManager } from "./fs"
 import { i18n } from "./i18n"
@@ -44,7 +45,9 @@ export class Vault {
    */
   static async of(path: string, profileName = "default", fs: IFileSystem) {
     const files = new OnePasswordFileManager(fs, path, profileName)
-    const profile = JSON.parse(stripText(await files.getProfile(), "var profile=", ";"))
+    const profile = JSON.parse(
+      stripText(await files.getProfile(), /^var profile\s*=/, ";")
+    )
     const folders = JSON.parse(stripText(await files.getFolders(), "loadFolders(", ");"))
     const bands = new Map<string, Band>()
 
@@ -111,7 +114,7 @@ export class Vault {
   }
 
   /**
-   * Remove derived keys within the class instance.
+   * Remove derived keys stored within the class instance.
    */
   lock() {
     this.#master = null!
@@ -171,6 +174,20 @@ function decryptItem(item: EncryptedItem, master: Cipher): Item {
   return JSON.parse(detail.toString("utf-8"))
 }
 
+function decryptAttachment(item: Buffer, master: Cipher) {
+  invariant(item.slice(0, 7).toString("utf-8") === "OPCLDA")
+  invariant(
+    item.readIntLE(7, 1) === 1,
+    "The version for this attachment file format is not supported."
+  )
+
+  const metadataSize = item.readIntLE(8, 2)
+  const iconSize = item.readIntLE(12, 3)
+
+  const metadata = JSON.parse(item.slice(16, 16 + metadataSize).toString("utf-8"))
+  const icondata = item.slice(16 + metadataSize, 16 + metadataSize + iconSize)
+}
+
 /** Encryption and MAC */
 interface Cipher {
   /** Encryption key */
@@ -179,9 +196,27 @@ interface Cipher {
   hmac: Buffer
 }
 
-function stripText(text: string, prefix: string, suffix: string) {
-  if (text.startsWith(prefix)) text = text.slice(prefix.length)
-  if (text.endsWith(suffix)) text = text.slice(0, -suffix.length)
+function stripText(text: string, prefix: string | RegExp, suffix: string | RegExp) {
+  if (typeof prefix === "string") {
+    if (text.startsWith(prefix)) {
+      text = text.slice(prefix.length)
+    }
+  } else {
+    const prefixMatch = text.match(prefix)
+    if (prefixMatch) {
+      text = text.slice(prefixMatch[0].length)
+    }
+  }
+  if (typeof suffix === "string") {
+    if (text.endsWith(suffix)) {
+      text = text.slice(0, -suffix.length)
+    }
+  } else {
+    const suffixMatch = text.match(suffix)
+    if (suffixMatch) {
+      text = text.slice(0, -suffixMatch[0].length)
+    }
+  }
   return text
 }
 
@@ -190,8 +225,6 @@ const splitPlainText = (derivedKey: Buffer): Cipher => ({
   hmac: derivedKey.slice(32, 64),
 })
 
-class HMACAssertionError extends Error {}
-
 function decryptOPData(cipherText: Buffer, cipher: Cipher) {
   const key = cipherText.slice(0, -32)
   assertHMac(key, cipher.hmac, cipherText.slice(-32))