良く忘れるのでメモ

using System;
using System.Text;
using System.Security.Cryptography;

namespace Musashi.WebApi_v1.Utility
{
    /// <summary>
    /// 暗号化・複合化を行う
    /// </summary>
    public static class Crypt
    {
        private static AesCryptoServiceProvider GetCryptInstance()
        {
            // AES暗号化サービスプロバイダ
            AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
            aes.BlockSize = 128;
            aes.KeySize = 256;
            aes.IV = Encoding.UTF8.GetBytes(任意の文字列);
            aes.Key = Encoding.UTF8.GetBytes(任意の文字列);
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;

            return aes;
        }

        // ラムダ式にしてみる
        public static byte[] CryptProcess(byte[] src, bool isEncrypt)
        {
            // AES暗号化サービスプロバイダ
            AesCryptoServiceProvider aes = GetCryptInstance();

            byte[] isOK = ((Func<byte[]>)(() => {using (ICryptoTransform encrypt = aes.CreateEncryptor()){return encrypt.TransformFinalBlock(src, 0, src.Length);}}))();

            // フラグによって暗号、復号の処理を分ける。
            return isEncrypt == true ?
                ((Func<byte[]>)(() => { using (ICryptoTransform encrypt = aes.CreateEncryptor()) { return encrypt.TransformFinalBlock(src, 0, src.Length); } }))() 
                :
                ((Func<byte[]>)(() => { using (ICryptoTransform decrypt = aes.CreateDecryptor()) { return decrypt.TransformFinalBlock(src, 0, src.Length); } }))();
        }


        /// <summary>
        /// AESで暗号化
        /// </summary>
        public static byte[] Encrypt(byte[] src)
        {
            // AES暗号化サービスプロバイダ
            AesCryptoServiceProvider aes = GetCryptInstance();

            // 暗号化する
            using (ICryptoTransform encrypt = aes.CreateEncryptor())
            {
                return encrypt.TransformFinalBlock(src, 0, src.Length);
            }
        }

        /// <summary>
        /// 文字列をAESで復号化
        /// </summary>
        public static byte[] Decrypt(byte[] src)
        {
            // AES暗号化サービスプロバイダ
            AesCryptoServiceProvider aes = GetCryptInstance();

            // 複号化する
            using (ICryptoTransform decrypt = aes.CreateDecryptor())
            {
                return decrypt.TransformFinalBlock(src, 0, src.Length);
            }
        }
    }
}

参考URL
https://msdn.microsoft.com/ja-jp/library/system.security.cryptography.aescryptoserviceprovider(v=vs.110).aspx
http://dalmore.blog7.fc2.com/blog-entry-37.html
http://programmers.high-way.info/cs/aes.html
http://qiita.com/hibara/items/c9096376b1d7b5c8e2ae

テスト
http://csrc.nist.gov/groups/STM/cavp/index.html

規格
https://www.ipa.go.jp/security/rfc/RFC3602JA.html