KMS & Envelope Encryption in AWS Serverless

1. Introduction

AWS Key Management Service (KMS) is a managed encryption service that allows you to create and control the encryption keys used to encrypt your data. Envelope Encryption is a method that combines symmetric and asymmetric encryption to enhance security and efficiency when encrypting large amounts of data.

2. What is KMS?

AWS KMS is a fully managed service that simplifies the process of creating and managing cryptographic keys. It also provides a centralized control over the keys used to encrypt your data, making it easier to comply with regulations and security standards.

3. What is Envelope Encryption?

Envelope Encryption is a technique where data is encrypted using a data encryption key (DEK), and the DEK itself is encrypted with a key encryption key (KEK). This allows you to encrypt large volumes of data efficiently while keeping the DEK secret.

4. Step-by-Step Implementation

Follow these steps to implement KMS and Envelope Encryption in your AWS Serverless application:

graph TD;
            A[Start] --> B[Generate Data Encryption Key (DEK)]
            B --> C[Encrypt Data with DEK]
            C --> D[Encrypt DEK with AWS KMS Key]
            D --> E[Store Encrypted DEK and Encrypted Data]
            E --> F[Done]
        

Step 1: Generate Data Encryption Key (DEK)

const AWS = require('aws-sdk');
const kms = new AWS.KMS();

async function generateDataEncryptionKey() {
    const params = {
        KeySpec: 'AES_256',
        NumberOfBytes: 32 // 256 bits
    };
    const dataKey = await kms.generateDataKey(params).promise();
    return dataKey;
}
        

Step 2: Encrypt Data with DEK

const crypto = require('crypto');

function encryptData(data, dataKey) {
    const iv = crypto.randomBytes(16);
    const cipher = crypto.createCipheriv('aes-256-cbc', dataKey, iv);
    let encryptedData = cipher.update(data, 'utf8', 'hex');
    encryptedData += cipher.final('hex');
    return { iv: iv.toString('hex'), encryptedData };
}
        

Step 3: Encrypt DEK with AWS KMS Key

async function encryptDataKey(dataKey) {
    const params = {
        KeyId: 'alias/myKeyAlias', // Replace with your KMS Key ID or Alias
        Plaintext: dataKey // The DEK that needs to be encrypted
    };
    const encryptedKey = await kms.encrypt(params).promise();
    return encryptedKey.CiphertextBlob;
}
        

Step 4: Store Encrypted DEK and Encrypted Data

Store the encryptedKey and encryptedData in your database or storage solution of choice.

5. Best Practices

• Use the least privilege principle when granting permissions to KMS keys.
• Enable automatic key rotation for enhanced security.
• Log key usage through AWS CloudTrail for audit and compliance.
• Consider using environment variables to manage sensitive data securely.

6. FAQ