RSA是常用的非对称加密算法。近来有学生在项目中使用System.Security类库中的RSA加密算法时，出现了“不正确的长度”，这实际上是因为待加密的数据超长所致。.net
Framework中提供的RSA算法规定，每次加密的字节数，不能超过密钥的长度值减去11,而每次加密得到的密文长度，却恰恰是密钥的长度。所以，如果要加密较长的数据，可以采用数据截取的方法，分段加密。或者增加自定义分块算法，进行加密。当然，你也可以加长密钥的长度，，呵呵。下面是分段加解密代码片段，希望对程序媛们有帮助
public override byte[] Encrypt(byte[] sourceBytes){CspParameters cspParams = new CspParameters();cspParams.KeyContainerName = KeyContainerName;RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(cspParams);int keySize = RSAalg.KeySize / 8;int bufferSize = keySize – 11;byte[] buffer = new byte[bufferSize];MemoryStream msInput = new MemoryStream(sourceBytes);MemoryStream msOutput = new MemoryStream();int readLen = msInput.Read(buffer, 0, bufferSize);while (readLen > 0){byte[] dataToEnc = new byte[readLen];Array.Copy(buffer, 0, dataToEnc, 0, readLen);byte[] encData = RSAalg.Encrypt(dataToEnc, false);msOutput.Write(encData, 0, encData.Length);readLen = msInput.Read(buffer, 0, bufferSize);}msInput.Close();byte[] result = msOutput.ToArray();//得到加密结果msOutput.Close();RSAalg.Clear();return result;//return RSAalg.Encrypt(sourceBytes, false);}public override byte[] Decrypt(byte[] cryptBytes){CspParameters cspParams = new CspParameters();cspParams.KeyContainerName = KeyContainerName;RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(cspParams);//return RSAalg.Decrypt(cryptBytes, false);int keySize = RSAalg.KeySize / 8;int bufferSize = keySize;// keySize – 11;byte[] buffer = new byte[bufferSize];MemoryStream msInput = new MemoryStream(cryptBytes);MemoryStream msOutput = new MemoryStream();int readLen = msInput.Read(buffer, 0, bufferSize);while (readLen > 0){byte[] dataToDec = new byte[readLen];Array.Copy(buffer, 0, dataToDec, 0, readLen);byte[] decData = RSAalg.Decrypt(dataToDec, false);msOutput.Write(decData, 0, decData.Length);readLen = msInput.Read(buffer, 0, bufferSize);}msInput.Close();byte[] result = msOutput.ToArray();//得到加密结果msOutput.Close();RSAalg.Clear();return result;}
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