Name space need to add from nuget packeg
using Amazon.KeyManagementService;
using Amazon.KeyManagementService.Model;
**1) Encryption :-**
AmazonKeyManagementServiceConfig kmsConfig = new AmazonKeyManagementServiceConfig();
kmsConfig.UseHttp = true;
kmsConfig.ServiceURL = serviceEndPoint;
//create client, specify Region end point or kms config
AmazonKeyManagementServiceClient kmsClient = new AmazonKeyManagementServiceClient(awsKeyForKMS, awsSecretKeyForKMS, kmsConfig);
GenerateDataKeyRequest dataKeyReq = new GenerateDataKeyRequest();
dataKeyReq.KeyId = keyARNForKMS;
dataKeyReq.KeySpec = DataKeySpec.AES_256;//The length of the data encryption key. AES_256 to generate a 256-bit symmetric key.
GenerateDataKeyResponse dataKeyResponse = kmsClient.GenerateDataKey(dataKeyReq);
//read encrypted data key from memory
MemoryStream streamCipherText = dataKeyResponse.CiphertextBlob;
// need to save this key with encrypted data because with the help of it
// you can decrypt(you got plaindatakey) the data
encryptedDataKey = Convert.ToBase64String(streamCipherText.ToArray());
//read plain data key from memory
MemoryStream streamPlainText = dataKeyResponse.Plaintext;
// use this key to encrypt your data and than forgot this key
plainDataKey = Convert.ToBase64String(streamPlainText.ToArray());
//your encryption logic
Encryption encrypt = new Encryption();
encrypt.EncryptTextForKms(PlainKey, "data to be encrypted")