Randomly Generating a Symmetric Key

This topic uses AES and SM4 as an example to describe how to generate a symmetric key and obtain the binary data.

The symmetric key (SymKey) object created can be used for subsequent encryption and decryption operations, and the binary data can be used for key storage and transfer.

Randomly Generating an AES Key

For details about the algorithm specifications, see AES.

  1. Use cryptoFramework.createSymKeyGenerator with the string parameter 'AES256' to create a symmetric key generator (SymKeyGenerator) object for a 256-bit AES key.

  2. Use SymKeyGenerator.generateSymKey to randomly generate a symmetric key (SymKey) object.

  3. Use SymKey.getEncoded to obtain the binary data of the key.

  • Example: Randomly generate a 256-bit AES key (using promise-based APIs).

    import cryptoFramework from '@ohos.security.cryptoFramework';

function testGenerateAesKey() {
  // Create a SymKeyGenerator instance.
  let symKeyGenerator = cryptoFramework.createSymKeyGenerator('AES256');
  // Use SymKeyGenerator to randomly generate a symmetric key.
  let promiseSymKey = symKeyGenerator.generateSymKey();
  promiseSymKey.then(key => {
    // Obtain the binary data of the symmetric key and output a 256-bit key, which is of 32 bytes.
    let encodedKey = key.getEncoded();
    console.info('key hex:' + encodedKey.data);
  });
}

Randomly Generating an SM4 Key

For details about the algorithm specifications, see SM4.

  1. Use cryptoFramework.createSymKeyGenerator with the string parameter 'SM4_128' to create a symmetric key generator (SymKeyGenerator) object for a 128-bit SM4 key. If you need to use other algorithms, modify the string parameter.

  2. Use SymKeyGenerator.generateSymKey to randomly generate a symmetric key (SymKey) object.

  3. Use SymKey.getEncoded to obtain the binary data of the key.

  • Example: Randomly generate a 128-bit SM4 key (using promise-based APIs).

    import cryptoFramework from '@ohos.security.cryptoFramework';

function testGenerateSM4Key() {
  // Create a SymKeyGenerator instance.
  let symKeyGenerator = cryptoFramework.createSymKeyGenerator('SM4_128');
  // Use SymKeyGenerator to randomly generate a symmetric key.
  let promiseSymKey = symKeyGenerator.generateSymKey();
  promiseSymKey.then(key => {
    // Obtain the binary data of the symmetric key and output a 128-bit byte stream, which is of 16 bytes.
    let encodedKey = key.getEncoded();
    console.info('key hex:' + encodedKey.data);
  });
}