Use GenerateRandom with an Amazon SDK or CLI

Example 1: To generate a 256-bit random byte string (Linux or macOs)

The following generate-random example generates a 256-bit (32-byte), base64-encoded random byte string. The example decodes the byte string and saves it in the random file.

When you run this command, you must use the number-of-bytes parameter to specify the length of the random value in bytes.

You don't specify a KMS key when you run this command. The random byte string is unrelated to any KMS key.

By default, Amazon KMS generates the random number. However, if you specify a custom key store<https://docs.aws.amazon.com/kms/latest/developerguide/custom-key-store-overview.html>, the random byte string is generated in the Amazon CloudHSM cluster associated with the custom key store.

This example uses the following parameters and values:

It uses the required --number-of-bytes parameter with a value of 32 to request a 32-byte (256-bit) string.It uses the --output parameter with a value of text to direct the Amazon CLI to return the output as text, instead of JSON.It uses the --query parameter to extract the value of the Plaintext property from the response.It pipes ( | ) the output of the command to the base64 utility, which decodes the extracted output.It uses the redirection operator ( > ) to save decoded byte string to the ExampleRandom file.It uses the redirection operator ( > ) to save the binary ciphertext to a file.

aws kms generate-random \
    --number-of-bytes 32 \
    --output text \
    --query Plaintext | base64 --decode > ExampleRandom

This command produces no output.

For more information, see GenerateRandom in the Amazon Key Management Service API Reference.

Example 2: To generate a 256-bit random number (Windows Command Prompt)

The following example uses the generate-random command to generate a 256-bit (32-byte), base64-encoded random byte string. The example decodes the byte string and saves it in the random file. This example is the same as the previous example, except that it uses the certutil utility in Windows to base64-decode the random byte string before saving it in a file.

First, generate a base64-encoded random byte string and saves it in a temporary file, ExampleRandom.base64.

aws kms generate-random \
    --number-of-bytes 32 \
    --output text \
    --query Plaintext > ExampleRandom.base64

Because the output of the generate-random command is saved in a file, this example produces no output.

Now use the certutil -decode command to decode the base64-encoded byte string in the ExampleRandom.base64 file. Then, it saves the decoded byte string in the ExampleRandom file.

certutil -decode ExampleRandom.base64 ExampleRandom

Output:

Input Length = 18
Output Length = 12
CertUtil: -decode command completed successfully.

For more information, see GenerateRandom in the Amazon Key Management Service API Reference.

async fn make_string(client: &Client, length: i32) -> Result<(), Error> {
    let resp = client
        .generate_random()
        .number_of_bytes(length)
        .send()
        .await?;

    // Did we get an encrypted blob?
    let blob = resp.plaintext.expect("Could not get encrypted text");
    let bytes = blob.as_ref();

    let s = base64::encode(bytes);

    println!();
    println!("Data key:");
    println!("{}", s);

    Ok(())
}