SubtleCrypto: decrypt() method

The decrypt() method of the {{domxref("SubtleCrypto")}} interface decrypts some encrypted data. It takes as arguments a {{glossary("key")}} to decrypt with, some optional extra parameters, and the data to decrypt (also known as "ciphertext"). It returns a {{jsxref("Promise")}} which will be fulfilled with the decrypted data (also known as "plaintext").

Syntax

js-nolint

decrypt(algorithm, key, data)

Parameters

algorithm
- : An object specifying the algorithm to be used, and any extra parameters as required. The values given for the extra parameters must match those passed into the corresponding {{domxref("SubtleCrypto.encrypt()", "encrypt()")}} call.
  - To use RSA-OAEP, pass an {{domxref("RsaOaepParams")}} object.
  - To use AES-CTR, pass an {{domxref("AesCtrParams")}} object.
  - To use AES-CBC, pass an {{domxref("AesCbcParams")}} object.
  - To use AES-GCM, pass an {{domxref("AesGcmParams")}} object.
key
- : A {{domxref("CryptoKey")}} containing the key to be used for decryption. If using RSA-OAEP, this is the privateKey property of the {{domxref("CryptoKeyPair")}} object.
data
- : An {{jsxref("ArrayBuffer")}}, a {{jsxref("TypedArray")}}, or a {{jsxref("DataView")}} containing the data to be decrypted (also known as {{glossary("ciphertext")}}).

Return value

A {{jsxref("Promise")}} that fulfills with an {{jsxref("ArrayBuffer")}} containing the plaintext.

Exceptions

The promise is rejected when the following exceptions are encountered:

InvalidAccessError {{domxref("DOMException")}}
- : Raised when the requested operation is not valid for the provided key (e.g., invalid encryption algorithm, or invalid key for the specified encryption algorithm).
OperationError {{domxref("DOMException")}}
- : Raised when the operation failed for an operation-specific reason (e.g., algorithm parameters of invalid sizes, or there was an error decrypting the ciphertext).

Supported algorithms

The decrypt() method supports the same algorithms as the encrypt() method.

Examples

[!NOTE] You can try the working examples on GitHub.

RSA-OAEP

This code decrypts ciphertext using RSA-OAEP. See the complete code on GitHub.

function decryptMessage(privateKey, ciphertext) {
  return window.crypto.subtle.decrypt(
    { name: "RSA-OAEP" },
    privateKey,
    ciphertext,
  );
}

AES-CTR

This code decrypts ciphertext using AES in CTR mode. Note that counter must match the value that was used for encryption. See the complete code on GitHub.

function decryptMessage(key, ciphertext) {
  return window.crypto.subtle.decrypt(
    { name: "AES-CTR", counter, length: 64 },
    key,
    ciphertext,
  );
}

AES-CBC

This code decrypts ciphertext using AES in CBC mode. Note that iv must match the value that was used for encryption. See the complete code on GitHub.

function decryptMessage(key, ciphertext) {
  // The iv value is the same as that used for encryption
  return window.crypto.subtle.decrypt({ name: "AES-CBC", iv }, key, ciphertext);
}

AES-GCM

This code decrypts ciphertext using AES in GCM mode. Note that iv must match the value that was used for encryption. See the complete code on GitHub.

function decryptMessage(key, ciphertext) {
  // The iv value is the same as that used for encryption
  return window.crypto.subtle.decrypt({ name: "AES-GCM", iv }, key, ciphertext);
}