新浪微博、qq等javascript rsa密码加密c#实现。

可用在新浪微博最新版的登录、qq注册、qq微博注册过程中的密码加密。

按js实现翻译过来的，为了对比方便，保留着js的命名。大数计算类BigInteger是c# 4.0才提供的，如果不想用这么高的版本，这里有个开源的实现：http://www.codeproject.com/csharp/biginteger.asp

public class JSRSAUtil
{
private static Random rand = new Random();

private BigInteger n = null;
private BigInteger e = null;

private BigInteger pkcs1pad2(string a, int b)
{
if (b < a.Length + 11)
{
throw new Exception("Message too long for RSA");
}

byte[] c = new byte[b];
int d = a.Length - 1;
while (d >= 0 && b > 0)
{
int e = (int)a[d--];
if (e < 128)
{
c[--b] = Convert.ToByte(e);
}
else if ((e > 127) && (e < 2048))
{
c[--b] = Convert.ToByte(((e & 63) | 128));
c[--b] = Convert.ToByte((e >> 6) | 192);
}
else
{
c[--b] = Convert.ToByte((e & 63) | 128);
c[--b] = Convert.ToByte(((e >> 6) & 63) | 128);
c[--b] = Convert.ToByte(((e >> 12) | 224));
}
}

c[--b] = Convert.ToByte(0);

byte[] temp = new byte[1];

while (b > 2)
{
temp[0] = Convert.ToByte(0);
while (temp[0] == 0)
rand.NextBytes(temp);
c[--b] = temp[0];
}

c[--b] = 2;
c[--b] = 0;

return new BigInteger(c);
}

public void RSASetPublic(string a, string b)
{
if (string.IsNullOrEmpty(a) || string.IsNullOrEmpty(b))
{
throw new Exception("Message too long for RSA");
}

n = new BigInteger(a, 16);
e = new BigInteger(b, 16);
}

private BigInteger RSADoPublic(BigInteger x)
{
return x.modPow(e, n);
}

public string RSAEncrypt(string a)
{
BigInteger tmp = pkcs1pad2(a, (n.bitCount() + 7) >> 3);

tmp = RSADoPublic(tmp);

string result = tmp.ToHexString();
return 0 == (result.Length & 1) ? result : "0" + result;
}
}

转自：http://pwg17.github.com/2012/12/16/weibo-qq-rsa-csharp/