C#/.NET字符串加密和解密实现(AES和RSA代码举例)

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在很多C#项目中,都需要实现对字符串的加密和解密，那么如何实现呢？现在对称密钥加密中最流行的就是AES加密法。

密码学中的高级加密标准（Advanced Encryption Standard，AES），又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。经过五年的甄选流程，高级加密标准由美国国家标准与技术研究院（NIST）于2001年11月26日发布于FIPS PUB 197，并在2002年5月26日成为有效的标准。2006年，高级加密标准已然成为对称密钥加密中最流行的算法之一。

在这里可以提供一个基于AES加密和解密的实现代码:

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public class Crypto

{

private static byte [] _salt = Encoding.ASCII.GetBytes( "o6806642kbM7c5" );

/// <summary>

/// Encrypt the given string using AES. The string can be decrypted using

/// DecryptStringAES(). The sharedSecret parameters must match.

/// </summary>

/// <param name="plainText">The text to encrypt.</param>

/// <param name="sharedSecret">A password used to generate a key for encryption.</param>

public static string EncryptStringAES( string plainText, string sharedSecret)

{

if ( string .IsNullOrEmpty(plainText))

throw new ArgumentNullException( "plainText" );

if ( string .IsNullOrEmpty(sharedSecret))

throw new ArgumentNullException( "sharedSecret" );

string outStr = null ; // Encrypted string to return

RijndaelManaged aesAlg = null ; // RijndaelManaged object used to encrypt the data.

try

{

// generate the key from the shared secret and the salt

Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

// Create a RijndaelManaged object

aesAlg = new RijndaelManaged();

aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

// Create a decryptor to perform the stream transform.

ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

// Create the streams used for encryption.

using (MemoryStream msEncrypt = new MemoryStream())

{

// prepend the IV

msEncrypt.Write(BitConverter.GetBytes(aesAlg.IV.Length), 0, sizeof ( int ));

msEncrypt.Write(aesAlg.IV, 0, aesAlg.IV.Length);

using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))

{

using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))

{

//Write all data to the stream.

swEncrypt.Write(plainText);

}

outStr = Convert.ToBase64String(msEncrypt.ToArray());

}

finally

{

// Clear the RijndaelManaged object.

if (aesAlg != null )

aesAlg.Clear();

}

// Return the encrypted bytes from the memory stream.

return outStr;

}

/// <summary>

/// Decrypt the given string. Assumes the string was encrypted using

/// EncryptStringAES(), using an identical sharedSecret.

/// </summary>

/// <param name="cipherText">The text to decrypt.</param>

/// <param name="sharedSecret">A password used to generate a key for decryption.</param>

public static string DecryptStringAES( string cipherText, string sharedSecret)

{

if ( string .IsNullOrEmpty(cipherText))

throw new ArgumentNullException( "cipherText" );

if ( string .IsNullOrEmpty(sharedSecret))

throw new ArgumentNullException( "sharedSecret" );

// Declare the RijndaelManaged object

// used to decrypt the data.

RijndaelManaged aesAlg = null ;

// Declare the string used to hold

// the decrypted text.

string plaintext = null ;

try

{

// generate the key from the shared secret and the salt

Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

// Create the streams used for decryption.

byte [] bytes = Convert.FromBase64String(cipherText);

using (MemoryStream msDecrypt = new MemoryStream(bytes))

{

// Create a RijndaelManaged object

// with the specified key and IV.

aesAlg = new RijndaelManaged();

aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

// Get the initialization vector from the encrypted stream

aesAlg.IV = ReadByteArray(msDecrypt);

// Create a decrytor to perform the stream transform.

ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))

{

using (StreamReader srDecrypt = new StreamReader(csDecrypt))

// Read the decrypted bytes from the decrypting stream

// and place them in a string.

plaintext = srDecrypt.ReadToEnd();

}

finally

{

// Clear the RijndaelManaged object.

if (aesAlg != null )

aesAlg.Clear();

}

return plaintext;

}

private static byte [] ReadByteArray(Stream s)

{

byte [] rawLength = new byte [ sizeof ( int )];

if (s.Read(rawLength, 0, rawLength.Length) != rawLength.Length)

{

throw new SystemException( "Stream did not contain properly formatted byte array" );

}

byte [] buffer = new byte [BitConverter.ToInt32(rawLength, 0)];

if (s.Read(buffer, 0, buffer.Length) != buffer.Length)

{

throw new SystemException( "Did not read byte array properly" );

}

return buffer;

}

另外再提供一段基于RSA的加密算法,RSA公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。RSA取名来自开发他们三者的名字。RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的所有密码攻击，已被ISO推荐为公钥数据加密标准。RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但那时想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。

C#中实现RSA加密代码如下:

var provider = new System.Security.Cryptography.RSACryptoServiceProvider();

provider.ImportParameters(your_rsa_key);

var encryptedBytes = provider.Encrypt(

System.Text.Encoding.UTF8.GetBytes( "Hello World!" ), true );

string decryptedTest = System.Text.Encoding.UTF8.GetString(

provider.Decrypt(encryptedBytes, true ));

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本文标题:C#/.NET字符串加密和解密实现(AES和RSA代码举例)

来源：oschina

链接：https://my.oschina.net/u/1766067/blog/300324

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高级加密标准

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