SubtleCrypto.decrypt

The SubtleCrypto.decrypt() method returns a Promise of the plaintext corresponding to the ciphertext data, algorithm and key given as parameters.

Syntax

var result = crypto.subtle.decrypt(algorithm, key, data);

Parameters

• algorithm is an object specifying the encryption function to be used and its parameters; if there are no parameters, algorithm can be a DOMString with the algorithm name. Supported values¹ are:
  • {"name": "AES-CBC", iv} where iv is as supplied to SubtleCrypto.encrypt().
  • {"name": "AES-CTR", counter, length} where counter and length are as supplied to SubtleCrypto.encrypt().
  • {"name": "AES-GCM", iv[, additionalData, tagLength]} where iv, additionalData, tagLength are as supplied to SubtleCrypto.encrypt().
  • {"name": "RSA-OAEP"[, label]} where label is as supplied to SubtleCrypto.encrypt().
• key is a CryptoKey containing the key to be used for decryption.
• data is a BufferSource containing the data to be decrypted, the ciphertext.

Return value

• result is a Promise that returns the plaintext generated by the decryption of the ciphertext.

Exceptions

The promise is rejected when the following exceptions are encountered:

InvalidAccessError

when the requested operation is not valid for the provided key (e.g. invalid encryption algorithm, or invalid key for specified encryption algorithm).

OperationError

when the operation failed for an operation-specific reason (e.g. algorithm parameters of invalid sizes, or the result of the decryption is a fail).

Example

const decryptText = async (ctBuffer, iv, password) => {
    const pwUtf8 = new TextEncoder().encode(password);
    const pwHash = await crypto.subtle.digest('SHA-256', pwUtf8);

    const alg = { name: 'AES-GCM', iv: iv };
    const key = await crypto.subtle.importKey('raw', pwHash, alg, false, ['decrypt']);

    const ptBuffer = await crypto.subtle.decrypt(alg, key, ctBuffer);

    const plaintext = new TextDecoder().decode(ptBuffer);

    return plaintext;
}

The iv is as supplied to SubtleCrypto.encrypt(); the ctBuffer is the ciphertext returned from SubtleCrypto.encrypt().

Specifications

Browser compatibilityUpdate compatibility data on GitHub

See also

• Crypto and Crypto.subtle.
• SubtleCrypto, the interface it belongs to.