Why am I receiving AWS.EncryptionSDK.AwsEncryptionSdkException "Failed to build header body". when trying to encrypt a string


Using the sample code below I receive the error on the line indicated in the comment below. I am able to encrypt and decrypt using the same key and account via aws kms cli.

public  MemoryStream EncryptMessageWithKMSKey(MemoryStream plaintext, string kmsKeyArn)
    var materialProviders =
    var encryptionSdk = AwsEncryptionSdkFactory.CreateDefaultAwsEncryptionSdk();
    var createKeyringInput = new CreateAwsKmsMrkMultiKeyringInput()
        Generator = kmsKeyArn
    var encryptionContext = new Dictionary<string, string>()
        {"purpose", "test"}
    var encryptKeyring = materialProviders.CreateAwsKmsMrkMultiKeyring(createKeyringInput);
    var encryptInput = new EncryptInput
        Plaintext = plaintext,
        Keyring = encryptKeyring,
        EncryptionContext = encryptionContext
    var encryptOutput = encryptionSdk.Encrypt(encryptInput);  // error here !!!!!!!!!!!!!!!!!!!!
    var ciphertext = encryptOutput.Ciphertext;
    return ciphertext;
  • Using AWS.EncryptionSDK 3.1.0 (latest at time of writing) AWSSDK.KeyManagamentService

  • The last log entry before it fails is AmazonKeyManagementServiceClient ... Received Response (truncated to 1024 bytes)

1 Answer

I am able to encrypt and decrypt using the same key and account via aws kms cli.

Are you referring to KMS CLI encrypt and decrypt? If so, you cannot use AWS Encryption SDK, which is a client-side encryption library, to decrypt a ciphertext that's encrypted by KMS directly. You have to use AWS SDK to call the KMS API with your payload. Unfortunately there isn't an example for encrypt and decrypt but think you should be able to piece it together (here's Python example if it helps).

Also this video: https://www.youtube.com/watch?v=YfoCNCuVSlI

answered 10 months ago

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