Added functions for encrypting/decrypting strings ↔ blobs (#11)

* added functions for encrypting/decrypting strings ↔ blobs

* deprecating base64 encrypt

src/index.test.ts

@@ -7,6 +7,8 @@ import {
   generateSalt,
   hash,
   hashPassword,
+  decryptBlobAsString,
+  encryptStringAsBlob,
 } from '.'
 
 import {arrayBufferToString, stringToArrayBuffer} from './utils'
@@ -122,3 +124,15 @@ it('sanity checks v001 ciphertext', async function () {
 
   expect(decrypted).toEqual(plaintext)
 })
+
+it('encrypts/decrypts blobs as strings', async function () {
+  const key = await generateEncryptionKey()
+
+  const plaintext = 'hello world'
+
+  const cipherblob = await encryptStringAsBlob({plaintext, key})
+
+  const decrypted = await decryptBlobAsString({cipherblob, key})
+
+  expect(decrypted).toEqual(plaintext)
+})

src/index.ts

@@ -51,6 +51,9 @@ export const generateSalt = () => {
  * @param key - In hex format
  * @param plaintext
  * @returns Base64 ciphertext string
+ *
+ * @deprecated This function converts cipherblob to base64 string, which is not
+ * efficient. Use one of the functions that return blob instead.
  */
 export const encrypt = async ({
   key,
@@ -70,6 +73,24 @@ export const encrypt = async ({
   return [Defaults.Version, nonce, ciphertext].join(STRING_PARTITION)
 }
 
+/**
+ * Encrypt a plaintext string and output it as a Uint8Array blob.
+ * @param key - The encryption key in hex format.
+ * @param plaintext - The plaintext string to encrypt.
+ * @returns A Promise that resolves to the encrypted message as a Uint8Array.
+ */
+export const encryptStringAsBlob = async ({
+  key,
+  plaintext,
+}: {
+  key: HexString
+  plaintext: Utf8String
+}): Promise<EncryptedBlobMessage> => {
+  const plainblob = await stringToArrayBuffer(plaintext)
+
+  return encryptBlob({key, plainblob})
+}
+
 /**
  * Encrypt a message (and associated data) with XChaCha20-Poly1305.
  * @param key - In hex format
@@ -119,6 +140,26 @@ export const decrypt = async ({
   return xChaChaDecrypt({key, ciphertext, nonce})
 }
 
+/**
+ * Decrypt an encrypted blob message and output it as a plaintext string.
+ * @param key - The decryption key in hex format.
+ * @param cipherblob - The encrypted message as a Uint8Array.
+ * @returns A Promise that resolves to the decrypted plaintext string or null if decryption fails.
+ */
+export const decryptBlobAsString = async ({
+  key,
+  cipherblob,
+}: {
+  key: HexString
+  cipherblob: EncryptedBlobMessage
+}): Promise<Utf8String | null> => {
+  const decryptedBlob = await decryptBlob({key, cipherblob})
+
+  if (!decryptedBlob) return null
+
+  return arrayBufferToString(decryptedBlob)
+}
+
 /**
  * Decrypt a message (and associated data) with XChaCha20-Poly1305
  * @param key - In hex format