rsa介绍
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的缺点:
-
产生密钥很麻烦，受到素数产生技术的限制，因而难以做到一次一密。
-
分组长度太大，为保证安全性，n 至少也要 600bits以上，使运算代价很高，尤其是速度较慢，较对称密码算法慢几个数量级；且随着大数分解技术的发展，这个长度还在增加，不利于数据格式的标准化。目前，set(secure electronic transaction)协议中要求ca采用2048bits长的密钥，其他实体使用1024比特的密钥。c)rsa密钥长度随着保密级别提高，增加很快。下表列出了对同一安全级别所对应的密钥长度。
保密级别 对称密钥长度（bit） rsa密钥长度（bit） ecc密钥长度（bit） 保密年限 80 80 1024 160 2010 112 112 2048 224 2030 128 128 3072 256 2040 192 192 7680 384 2080 256 256 15360 512 2120
c#中rsa的相关操作
- 生成公钥和私钥
struct rsasecretkey
{
public rsasecretkey(string privatekey, string publickey)
{
privatekey = privatekey;
publickey = publickey;
}
public string publickey { get; set; }
public string privatekey { get; set; }
public override string tostring()
{
return string.format(
"privatekey: {0}\r\npublickey: {1}", privatekey, publickey);
}
}
/// <summary>
/// generate rsa secret key
/// </summary>
/// <param name="keysize">the size of the key,must from 384 bits to 16384 bits in increments of 8 </param>
/// <returns></returns>
rsasecretkey generatersasecretkey(int keysize)
{
rsasecretkey rsakey = new rsasecretkey();
using (rsacryptoserviceprovider rsa = new rsacryptoserviceprovider(keysize))
{
rsakey.privatekey = rsa.toxmlstring(true);
rsakey.publickey = rsa.toxmlstring(false);
}
return rsakey;
}
- 实现公钥加密私钥解密
string rsaencrypt(string xmlpublickey,string content)
{
string encryptedcontent = string.empty;
using(rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsa.fromxmlstring(xmlpublickey);
byte[] encrypteddata = rsa.encrypt(encoding.default.getbytes(content), false);
encryptedcontent = convert.tobase64string(encrypteddata);
}
return encryptedcontent;
}
string rsadecrypt(string xmlprivatekey, string content)
{
string decryptedcontent = string.empty;
using (rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsa.fromxmlstring(xmlprivatekey);
byte[] decrypteddata = rsa.decrypt(convert.frombase64string(content), false);
decryptedcontent = encoding.getencoding("gb2312").getstring(decrypteddata);
}
return decryptedcontent;
}
密钥格式的转换
c#中rsa公钥和私钥的格式都是xml的,而在其他语言如java中,生成的rsa密钥就是普通的base64字符串,所以需要将c#xml格式的密钥转换成普通的base64字符串,同时也要实现base64密钥字符串生成c#中xml格式的密钥.
安装 bouncycastle 这个nuget包
pm > install-package bouncycastle
bouncycastle项目网址
bouncycastlegithub地址
构造一个rsakeyconventer类
namespace rsa
{
using system;
using system.security.cryptography;
using org.bouncycastle.asn1.pkcs;
using org.bouncycastle.math;
using org.bouncycastle.pkcs;
using org.bouncycastle.asn1.x509;
using org.bouncycastle.x509;
using org.bouncycastle.security;
using org.bouncycastle.crypto.parameters;
public class rsakeyconverter
{
/// <summary>
/// xml private key -> base64 private key string
/// </summary>
/// <param name="xmlprivatekey"></param>
/// <returns></returns>
public static string fromxmlprivatekey(string xmlprivatekey)
{
string result = string.empty;
using(rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsa.fromxmlstring(xmlprivatekey);
rsaparameters param = rsa.exportparameters(true);
rsaprivatecrtkeyparameters privatekeyparam = new rsaprivatecrtkeyparameters(
new biginteger(1, param.modulus), new biginteger(1, param.exponent),
new biginteger(1, param.d), new biginteger(1, param.p),
new biginteger(1, param.q), new biginteger(1, param.dp),
new biginteger(1, param.dq), new biginteger(1, param.inverseq));
privatekeyinfo privatekey = privatekeyinfofactory.createprivatekeyinfo(privatekeyparam);
result = convert.tobase64string(privatekey.toasn1object().getencoded());
}
return result;
}
/// <summary>
/// xml public key -> base64 public key string
/// </summary>
/// <param name="xmlpublickey"></param>
/// <returns></returns>
public static string fromxmlpublickey(string xmlpublickey)
{
string result = string.empty;
using(rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsa.fromxmlstring(xmlpublickey);
rsaparameters p = rsa.exportparameters(false);
rsakeyparameters keyparams = new rsakeyparameters(
false, new biginteger(1,p.modulus), new biginteger(1, p.exponent));
subjectpublickeyinfo publickeyinfo = subjectpublickeyinfofactory.createsubjectpublickeyinfo(keyparams);
result = convert.tobase64string(publickeyinfo.toasn1object().getencoded());
}
return result;
}
/// <summary>
/// base64 private key string -> xml private key
/// </summary>
/// <param name="privatekey"></param>
/// <returns></returns>
public static string toxmlprivatekey(string privatekey)
{
rsaprivatecrtkeyparameters privatekeyparams =
privatekeyfactory.createkey(convert.frombase64string(privatekey)) as rsaprivatecrtkeyparameters;
using(rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsaparameters rsaparams = new rsaparameters()
{
modulus = privatekeyparams.modulus.tobytearrayunsigned(),
exponent = privatekeyparams.publicexponent.tobytearrayunsigned(),
d = privatekeyparams.exponent.tobytearrayunsigned(),
dp = privatekeyparams.dp.tobytearrayunsigned(),
dq = privatekeyparams.dq.tobytearrayunsigned(),
p = privatekeyparams.p.tobytearrayunsigned(),
q = privatekeyparams.q.tobytearrayunsigned(),
inverseq = privatekeyparams.qinv.tobytearrayunsigned()
};
rsa.importparameters(rsaparams);
return rsa.toxmlstring(true);
}
}
/// <summary>
/// base64 public key string -> xml public key
/// </summary>
/// <param name="pubilckey"></param>
/// <returns></returns>
public static string toxmlpublickey(string pubilckey)
{
rsakeyparameters p =
publickeyfactory.createkey(convert.frombase64string(pubilckey)) as rsakeyparameters;
using(rsacryptoserviceprovider rsa = new rsacryptoserviceprovider())
{
rsaparameters rsaparams = new rsaparameters
{
modulus = p.modulus.tobytearrayunsigned(),
exponent = p.exponent.tobytearrayunsigned()
};
rsa.importparameters(rsaparams);
return rsa.toxmlstring(false);
}
}
}
}
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