《关于RSA加密算法的长度限制问题.docx》由会员分享,可在线阅读,更多相关《关于RSA加密算法的长度限制问题.docx(3页珍藏版)》请在三一办公上搜索。
1、关于RSA加密算法的长度限制问题关于RSA加密算法的长度限制问题 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,实现如下: RSACryptoServiceProvider rsa = new RSACryptoServiceProvider; byte data =
2、.; /要加密的数据 string publicKey = . ; /获取公钥 rsa.FromXmlString(publicKey); int keySize = rsa.KeySize / 8; int bufferSize = keySize - 11; byte buffer = new bytebufferSize; MemoryStream msInput = new MemoryStream(data); MemoryStream msOuput = new MemoryStream; int readLen = msInput.Read(buffer, 0, bufferSi
3、ze); while(readLen 0) byte dataToEnc = new bytereadLen; Array.Copy(buffer, 0 , dataToEnc, 0, readLen); byte encData = rsa.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 msOu
4、tput.Close; rsa.Clear; 解密时肯定也要使用分段解密,算法如下: RSACryptoServiceProvider rsa = new RSACryptoServiceProvider; byte key = .; /加载私钥 string privateKey = Encoding.ASCII.GetString(key); byte dataEnc = .; /加载密文 rsa.FromXmlString(privateKey); int keySize = rsa.KeySize / 8; byte buffer = new bytekeySize; MemorySt
5、ream msInput = new MemoryStream(dataEnc ); MemoryStream msOuput = new MemoryStream; int readLen = msInput.Read(buffer, 0, keySize); while(readLen 0) byte dataToDec = new bytereadLen; Array.Copy(buffer, 0 , dataToDec, 0, readLen); byte decData = rsa.Decrypt(dataToDec , false); msOutput.Write(decData, 0, decData.Length); readLen = msInput.Read(buffer, 0, keySize); msInput.Close; byte result = msOutput.ToArray; /得到解密结果 msOutput.Close; rsa.Clear;