SubtleCrypto: decrypt() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

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

Syntax

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 encrypt() call.

To use RSA-OAEP, pass an RsaOaepParams object.
To use AES-CTR, pass an AesCtrParams object.
To use AES-CBC, pass an AesCbcParams object.
To use AES-GCM, pass an AesGcmParams object.

key

A CryptoKey containing the key to be used for decryption. If using RSA-OAEP, this is the privateKey property of the CryptoKeyPair object.

data

An ArrayBuffer, a TypedArray, or a DataView containing the data to be decrypted (also known as ciphertext).

Return value

A Promise that fulfills with an ArrayBuffer containing the plaintext.

Exceptions

The promise is rejected when the following exceptions are encountered:

InvalidAccessError 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 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).

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);
}

Specifications

Specification
Web Cryptography API # SubtleCrypto-method-decrypt

Browser compatibility

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