Example code for the DynamoDB Encryption Client for Java

Create an instance of the AWS KMS client with the specified region. Then, use the client instance to create an instance of the Direct KMS Provider with your preferred AWS KMS key.

This example uses the Amazon Resource Name (ARN) to identify the AWS KMS key, but you can use any valid key identifier.

final String keyArn = "arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab";
final String region = "us-west-2";
      
final AWSKMS kms = AWSKMSClientBuilder.standard().withRegion(region).build();
final DirectKmsMaterialProvider cmp = new DirectKmsMaterialProvider(kms, keyArn);

This example defines a record HashMap that represents a sample table item.

final String partitionKeyName = "partition_attribute";
final String sortKeyName = "sort_attribute";

final Map<String, AttributeValue> record = new HashMap<>();
record.put(partitionKeyName, new AttributeValue().withS("value1"));
record.put(sortKeyName, new AttributeValue().withN("55"));
record.put("example", new AttributeValue().withS("data"));
record.put("numbers", new AttributeValue().withN("99"));
record.put("binary", new AttributeValue().withB(ByteBuffer.wrap(new byte[]{0x00, 0x01, 0x02})));
record.put("test", new AttributeValue().withS("test-value"));

Create an instance of the DynamoDBEncryptor with the Direct KMS Provider.

final DynamoDBEncryptor encryptor = DynamoDBEncryptor.getInstance(cmp);

The DynamoDB encryption context contains information about the table structure and how it is encrypted and signed. If you use the DynamoDBMapper, the AttributeEncryptor creates the encryption context for you.

final String tableName = "testTable";

final EncryptionContext encryptionContext = new EncryptionContext.Builder()
    .withTableName(tableName)
    .withHashKeyName(partitionKeyName)
    .withRangeKeyName(sortKeyName)
    .build();

Attribute actions determine which attributes of the item are encrypted and signed, which are only signed, and which are not encrypted or signed.

In Java, to specify attribute actions, you create a HashMap of attribute name and EncryptionFlags value pairs.

For example, the following Java code creates an actions HashMap that encrypts and signs all attributes in the record item, except for the partition key and sort key attributes, which are signed, but not encrypted, and the test attribute, which is not signed or encrypted.

final EnumSet<EncryptionFlags> signOnly = EnumSet.of(EncryptionFlags.SIGN);
final EnumSet<EncryptionFlags> encryptAndSign = EnumSet.of(EncryptionFlags.ENCRYPT, EncryptionFlags.SIGN);
final Map<String, Set<EncryptionFlags>> actions = new HashMap<>();

for (final String attributeName : record.keySet()) {
  switch (attributeName) {
    case partitionKeyName: // fall through to the next case
    case sortKeyName:
      // Partition and sort keys must not be encrypted, but should be signed
      actions.put(attributeName, signOnly);
      break;
    case "test":
      // Neither encrypted nor signed
      break;
    default:
      // Encrypt and sign all other attributes
      actions.put(attributeName, encryptAndSign);
      break;
  }
}

To encrypt and sign the table item, call the encryptRecord method on the instance of the DynamoDBEncryptor. Specify the table item (record), the attribute actions (actions), and the encryption context (encryptionContext).

final Map<String, AttributeValue> encrypted_record = encryptor.encryptRecord(record, actions, encryptionContext);

Finally, put the encrypted and signed item in the DynamoDB table.

final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.defaultClient();
ddb.putItem(tableName, encrypted_record);

Create an instance of the AWS KMS client with the specified region. Then, use the client instance to create an instance of the Direct KMS Provider with your preferred AWS KMS key.

This example uses the Amazon Resource Name (ARN) to identify the AWS KMS key, but you can use any valid key identifier.

final String keyArn = "arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab";
final String region = "us-west-2";
      
final AWSKMS kms = AWSKMSClientBuilder.standard().withRegion(region).build();
final DirectKmsMaterialProvider cmp = new DirectKmsMaterialProvider(kms, keyArn);

Use the Direct KMS Provider that you created in the previous step to create an instance of the DynamoDB Encryptor. You need to instantiate the lower-level DynamoDB Encryptor to use the DynamoDB Mapper.

Next, create an instance of your DynamoDB database and a mapper configuration, and use them to create an instance of the DynamoDB Mapper.

final DynamoDBEncryptor encryptor = DynamoDBEncryptor.getInstance(cmp)
final AmazonDynamoDB ddb = AmazonDynamoDBClientBuilder.standard().withRegion(region).build();

DynamoDBMapperConfig mapperConfig = DynamoDBMapperConfig.builder().withSaveBehavior(SaveBehavior.PUT).build();
DynamoDBMapper mapper = new DynamoDBMapper(ddb, mapperConfig, new AttributeEncryptor(encryptor));

Next, define your DynamoDB table. Use annotations to specify the attribute actions. This example creates a DynamoDB table, ExampleTable, and a DataPoJo class that represents table items.

In this sample table, the primary key attributes will be signed but not encrypted. This applies to the partition_attribute, which is annotated with @DynamoDBHashKey, and the sort_attribute, which is annotated with @DynamoDBRangeKey.

Attributes that are annotated with @DynamoDBAttribute, such as some numbers, will be encrypted and signed. The exceptions are attributes that use the @DoNotEncrypt (sign only) or @DoNotTouch (do not encrypt or sign) encryption annotations defined by the DynamoDB Encryption Client. For example, because the leave me attribute has a @DoNotTouch annotation, it will not be encrypted or signed.

@DynamoDBTable(tableName = "ExampleTable")
public static final class DataPoJo {
  private String partitionAttribute;
  private int sortAttribute;
  private String example;
  private long someNumbers;
  private byte[] someBinary;
  private String leaveMe;

  @DynamoDBHashKey(attributeName = "partition_attribute")
  public String getPartitionAttribute() {
    return partitionAttribute;
  }

  public void setPartitionAttribute(String partitionAttribute) {
    this.partitionAttribute = partitionAttribute;
  }

  @DynamoDBRangeKey(attributeName = "sort_attribute")
  public int getSortAttribute() {
    return sortAttribute;
  }

  public void setSortAttribute(int sortAttribute) {
    this.sortAttribute = sortAttribute;
  }

  @DynamoDBAttribute(attributeName = "example")
  public String getExample() {
    return example;
  }

  public void setExample(String example) {
    this.example = example;
  }

  @DynamoDBAttribute(attributeName = "some numbers")
  public long getSomeNumbers() {
    return someNumbers;
  }

  public void setSomeNumbers(long someNumbers) {
    this.someNumbers = someNumbers;
  }

  @DynamoDBAttribute(attributeName = "and some binary")
  public byte[] getSomeBinary() {
    return someBinary;
  }

  public void setSomeBinary(byte[] someBinary) {
    this.someBinary = someBinary;
  }

  @DynamoDBAttribute(attributeName = "leave me")
  @DoNotTouch
  public String getLeaveMe() {
    return leaveMe;
  }

  public void setLeaveMe(String leaveMe) {
    this.leaveMe = leaveMe;
  }

  @Override
  public String toString() {
    return "DataPoJo [partitionAttribute=" + partitionAttribute + ", sortAttribute="
        + sortAttribute + ", example=" + example + ", someNumbers=" + someNumbers
        + ", someBinary=" + Arrays.toString(someBinary) + ", leaveMe=" + leaveMe + "]";
  }
}

Now, when you create a table item and use the DynamoDB Mapper to save it, the item is automatically encrypted and signed before it is added to the table.

This example defines a table item called record. Before it is saved in the table, its attributes are encrypted and signed based on the annotations in the DataPoJo class. In this case, all attributes except for PartitionAttribute, SortAttribute, and LeaveMe are encrypted and signed. PartitionAttribute and SortAttributes are only signed. The LeaveMe attribute is not encrypted or signed.

To encrypt and sign the record item, and then add it to the ExampleTable, call the save method of the DynamoDBMapper class. Because your DynamoDB Mapper is configured to use the PUT save behavior, the item replaces any item with the same primary keys, instead of updating it. This ensures that the signatures match and you can decrypt the item when you get it from the table.

DataPoJo record = new DataPoJo();
record.setPartitionAttribute("is this");
record.setSortAttribute(55);
record.setExample("data");
record.setSomeNumbers(99);
record.setSomeBinary(new byte[]{0x00, 0x01, 0x02});
record.setLeaveMe("alone");

mapper.save(record);