Asymmetric data encryption

In this section, you will learn how to use KMS to encrypt and decrypt data using asymmetric encryption.

Getting startedGetting started

This guide uses OpenSSL for encrypting data through the Bash command line. If you do not have OpenSSL yet, install it.

sudo apt-get install openssl

choco install openssl

Encrypt dataEncrypt data

1. If you do not have an encryption key pair, create one.

2. Get a public encryption key and save it:

   Management console

   CLI

   API

   1. In the management console, select the folder with the appropriate key pair.
   2. In the list of services, select Key Management Service.
   3. In the left-hand panel, select Asymmetric keys.
   4. Go to the Encryption tab.
   5. In the line with the key pair, click and select Public key.
   6. In the window that opens, click Download to download a public encryption key.

   If you do not have the Yandex Cloud command line interface yet, install and initialize it.

   The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

   1. See the description of the CLI command to get a public encryption key:

      yc kms asymmetric-encryption-crypto get-public-key --help
      

   2. Get the ID of the folder where the encryption key pair is saved.

   3. Get the ID of the required encryption key pair by specifying the folder ID:

      yc kms asymmetric-encryption-key list \
        --folder-id <folder_ID>
      

      Result:

      +----------------------+-----------------------+---------------------------+---------------------+--------+
      |          ID          |          NAME         |   ENCRYPTION ALGORITHM    |     CREATED AT      | STATUS |
      +----------------------+-----------------------+---------------------------+---------------------+--------+
      | abjfmo5enqlr******** | sample-encryption-key | RSA_2048_ENC_OAEP_SHA_256 | 2023-08-16 18:10:03 | ACTIVE |
      +----------------------+-----------------------+---------------------------+---------------------+--------+
      

   4. Get a public encryption key by specifying the previously obtained key pair ID:

      yc kms asymmetric-encryption-crypto get-public-key \
        --id <key_pair_ID>
      

      Result:

      key_id: abj9g2dil5sj********
      public_key: |
      -----BEGIN PUBLIC KEY-----
      MIIB...
      ...QAB
      -----END PUBLIC KEY-----
      

      Save this key to a file, e.g., public.key. Make sure that lines in the file do not start with spaces.

   To get a public encryption key, use the AsymmetricEncryptionCryptoService/GetPublicKey gRPC API call.

3. Encrypt the message file:

   Note

   The size of a message to encrypt depends on the length of an encryption key and hash function.

   Bash

   Java

   Go

   Python

   In the terminal, run this command:

   openssl pkeyutl \
     -in <message_file_path> \
     -encrypt \
     -pubin \
     -inkey <public_key_file_path> \
     -pkeyopt rsa_padding_mode:oaep \
     -pkeyopt rsa_oaep_md:sha256 \
     -pkeyopt rsa_mgf1_md:sha256 | base64 > <ciphertext_file_path>
   

   Where:

   • -in: Path to the file with the message to encrypt.
   • -inkey: Path to the file with the public encryption key.
   • <ciphertext_file_path>: Path to the file the encrypted message will be saved to.

   As a result, the encrypted message will be saved to the specified file in the base64 encoding.

   import org.bouncycastle.util.io.pem.PemObject;
   import org.bouncycastle.util.io.pem.PemReader;
   
   import javax.crypto.BadPaddingException;
   import javax.crypto.Cipher;
   import javax.crypto.IllegalBlockSizeException;
   import javax.crypto.NoSuchPaddingException;
   import java.io.IOException;
   import java.io.StringReader;
   import java.security.*;
   import java.security.spec.*;
   import java.util.Base64;
   
   public class EncryptRsa {
       public static void main(String[] args) throws Exception {
           String plaintext = "<message>";
           String publicKeyPem = """
           -----BEGIN PUBLIC KEY-----
           <public_key_contents>
           -----END PUBLIC KEY-----""";
           byte[] cipherTextBytes = encryptWithRsaOaep(plaintext, publicKeyPem);
           System.out.println(Base64.getEncoder().encodeToString(cipherTextBytes));
       }
   
       private static byte[] encryptWithRsaOaep(String plaintext, String publicKeyPem)
       throws IOException, NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException,
       InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
   
           // Parsing PEM-encoded public key
           PemReader pemReader = new PemReader(new StringReader(publicKeyPem));
           PemObject pemObject = pemReader.readPemObject();
           byte[] publicKeyBytes = pemObject.getContent();
   
           // Creating a PublicKey object from encoded key bytes
           X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes);
           KeyFactory keyFactory = KeyFactory.getInstance("RSA");
           PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
   
           // Creating a Cipher object for encryption
           Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");
           cipher.init(Cipher.ENCRYPT_MODE, publicKey);
   
           // Text encryption
           byte[] plaintextBytes = plaintext.getBytes();
   
           // return cipher bytes
           return cipher.doFinal(plaintextBytes);
       }
   }
   

   Where:

   • <message_text>: Message text to encrypt.
   • <public_key_contents>: Contents of the public encryption key.

   Encryption is based on the RSA algorithm using OAEPand SHA-256. The code will return ciphertext as a string in base64 encoding.

    import (
       "crypto"
       "crypto/rand"
       "crypto/rsa"
       "crypto/x509"
       "encoding/pem"
       "fmt"
       "log"
   )
   
   func runRsaEncryption() {
       plaintext := "<message>"
       publicKeyPem := `-----BEGIN PUBLIC KEY-----
       <public_key_contents>
       -----END PUBLIC KEY-----`
       ciphertextBytes := encryptRSA(publicKeyPem, plaintext, crypto.SHA256)
       ciphertextBase64 := base64.StdEncoding.EncodeToString(ciphertextBytes)
   
           fmt.Println("Ciphertext:", ciphertextBase64)
   }
   
   func encryptRSA(publicKeyPem string, plaintext string, hash crypto.Hash) []byte {
   
       block, _ := pem.Decode([]byte(publicKeyPem))
       if block == nil {
           log.Fatal("failed to decode PEM block containing public key")
       }
   
       pub, err := x509.ParsePKIXPublicKey(block.Bytes)
       if err != nil {
   	    log.Fatal(err)
       }
   
       publicKey, ok := pub.(*rsa.PublicKey)
       if !ok {
   	    log.Fatal("not RSA public key")
       }
   
       ciphertext, err := rsa.EncryptOAEP(hash.New(), rand.Reader, publicKey, []byte(plaintext), nil)
       if err != nil {
   	    log.Fatal(err)
       }
   
       return ciphertext
   }
   

   Where:

   • <message_text>: Message text to encrypt.
   • <public_key_contents>: Contents of the public encryption key.

   Encryption is based on the RSA algorithm using OAEPand SHA-256. The code will return ciphertext as a string in base64 encoding.

   from cryptography.hazmat.primitives.asymmetric import rsa, padding
   from cryptography.hazmat.primitives import hashes
   from cryptography.hazmat.primitives import serialization
   
   # Define hash algorithms and corresponding salt lengths
   def encrypt_with_rsa_oaep(plaintext, public_key_string, hash_algorithm):
       hash_algorithms = {
           'SHA256': hashes.SHA256,
           'SHA384': hashes.SHA384,
           'SHA512': hashes.SHA512
       }
   
       # Check if the provided hash algorithm is supported
       if hash_algorithm not in hash_algorithms:
           raise ValueError('Unsupported hash algorithm: ' + hash_algorithm)
   
       # Loading a PEM Encoded Public Key
       public_key = serialization.load_pem_public_key(
           public_key_string.encode()
       )
   
       # Text encryption
       ciphertext = public_key.encrypt(
           plaintext.encode(),
           padding.OAEP(
               mgf=padding.MGF1(algorithm=hash_algorithms[hash_algorithm]()),
               algorithm=hash_algorithms[hash_algorithm](),
               label=None
           )
       )
   
       # Return ciphertext in Byte array format
       return ciphertext
   
   def test_encrypt_text():
       plaintext = "<message>"
       public_key_string = """
       -----BEGIN PUBLIC KEY-----
       <public_key_contents>
       -----END PUBLIC KEY-----"""
       ciphertext = encrypt_with_rsa_oaep(plaintext, public_key_string,'SHA256')
       ciphertext_base64 = base64.b64encode(ciphertext).decode()
       print("Ciphertext:", ciphertext_base64)
   

   Where:

   • <message_text>: Message text to encrypt.
   • <public_key_contents>: Contents of the public encryption key.

   Encryption is based on the RSA algorithm using OAEPand SHA-256. The code will return ciphertext as a string in base64 encoding.

Decrypt dataDecrypt data