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[英]Unable to decrypt a string in C# which is encrypted with RSA public key in Node.js
[英]Issue decrypting RSA public-key encrypted data by JS in C#
我收到錯誤在 C# 中解密 RSA 加密字符串時The data to be decrypted exceeds the maximum for this modulus of 256 bytes
。
我正在努力實現的目標:
什么工作:
到目前為止編寫的代碼:
C#
///Source: https://stackoverflow.com/questions/17128038/c-sharp-rsa-encryption-decryption-with-transmission
public static void GenerateKeys()
{
//CSP with a new 2048 bit rsa key pair
var csp = new RSACryptoServiceProvider(2048);
//Private key
var privKey = csp.ExportParameters(true);
//Public key
var pubKey = csp.ExportParameters(false);
string privKeyString = string.Empty;
var sw = new System.IO.StringWriter();
var xs = new System.Xml.Serialization.XmlSerializer(typeof(RSAParameters));
xs.Serialize(sw, privKey);
privKeyString = sw.ToString();
//This will give public key in the following format which is required by the JS library
//-----BEGIN PUBLIC KEY-----
//XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
//-----END PUBLIC KEY-----
string publicKeyBase64 = ConvertPublicKeyForJS(pubKey);
//Will be saved in sesssion for later use during decryption
string privateKeyBase64 = Convert.ToBase64String(System.Text.Encoding.ASCII.GetBytes(privKeyString));
//Save in session/temp location
//Return publicKeyBase64 to JS
}
/// <summary>
/// Source: https://stackoverflow.com/questions/28406888/c-sharp-rsa-public-key-output-not-correct/28407693#28407693
/// </summary>
/// <param name="publicKey"></param>
/// <returns></returns>
public static string ConvertPublicKeyForJS(RSAParameters publicKey)
{
string output = string.Empty;
using (var stream = new MemoryStream())
{
var writer = new BinaryWriter(stream);
writer.Write((byte)0x30); // SEQUENCE
using (var innerStream = new MemoryStream())
{
var innerWriter = new BinaryWriter(innerStream);
innerWriter.Write((byte)0x30); // SEQUENCE
EncodeLength(innerWriter, 13);
innerWriter.Write((byte)0x06); // OBJECT IDENTIFIER
var rsaEncryptionOid = new byte[] { 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01 };
EncodeLength(innerWriter, rsaEncryptionOid.Length);
innerWriter.Write(rsaEncryptionOid);
innerWriter.Write((byte)0x05); // NULL
EncodeLength(innerWriter, 0);
innerWriter.Write((byte)0x03); // BIT STRING
using (var bitStringStream = new MemoryStream())
{
var bitStringWriter = new BinaryWriter(bitStringStream);
bitStringWriter.Write((byte)0x00); // # of unused bits
bitStringWriter.Write((byte)0x30); // SEQUENCE
using (var paramsStream = new MemoryStream())
{
var paramsWriter = new BinaryWriter(paramsStream);
EncodeIntegerBigEndian(paramsWriter, publicKey.Modulus); // Modulus
EncodeIntegerBigEndian(paramsWriter, publicKey.Exponent); // Exponent
var paramsLength = (int)paramsStream.Length;
EncodeLength(bitStringWriter, paramsLength);
bitStringWriter.Write(paramsStream.GetBuffer(), 0, paramsLength);
}
var bitStringLength = (int)bitStringStream.Length;
EncodeLength(innerWriter, bitStringLength);
innerWriter.Write(bitStringStream.GetBuffer(), 0, bitStringLength);
}
var length = (int)innerStream.Length;
EncodeLength(writer, length);
writer.Write(innerStream.GetBuffer(), 0, length);
}
var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length);
StringBuilder sb = new StringBuilder();
sb.AppendLine("-----BEGIN PUBLIC KEY-----");
sb.AppendLine(base64);
sb.AppendLine("-----END PUBLIC KEY-----");
output = sb.ToString();
}
return output;
}
private static void EncodeLength(BinaryWriter stream, int length)
{
if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
if (length < 0x80)
{
// Short form
stream.Write((byte)length);
}
else
{
// Long form
var temp = length;
var bytesRequired = 0;
while (temp > 0)
{
temp >>= 8;
bytesRequired++;
}
stream.Write((byte)(bytesRequired | 0x80));
for (var i = bytesRequired - 1; i >= 0; i--)
{
stream.Write((byte)(length >> (8 * i) & 0xff));
}
}
}
private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true)
{
stream.Write((byte)0x02); // INTEGER
var prefixZeros = 0;
for (var i = 0; i < value.Length; i++)
{
if (value[i] != 0) break;
prefixZeros++;
}
if (value.Length - prefixZeros == 0)
{
EncodeLength(stream, 1);
stream.Write((byte)0);
}
else
{
if (forceUnsigned && value[prefixZeros] > 0x7f)
{
// Add a prefix zero to force unsigned if the MSB is 1
EncodeLength(stream, value.Length - prefixZeros + 1);
stream.Write((byte)0);
}
else
{
EncodeLength(stream, value.Length - prefixZeros);
}
for (var i = prefixZeros; i < value.Length; i++)
{
stream.Write(value[i]);
}
}
}
public static string DecryptValue(string cypherText)
{
string plainTextData = string.Empty;
string privKeyBase64 = ""; //get value from session/temp storage
string privKeyString = System.Text.Encoding.ASCII.GetString(Convert.FromBase64String(privKeyBase64));
var sr = new System.IO.StringReader(privKeyString);
var xs = new System.Xml.Serialization.XmlSerializer(typeof(RSAParameters));
var privKey = (RSAParameters)xs.Deserialize(sr);
var csp = new RSACryptoServiceProvider();
csp.ImportParameters(privKey);
var bytesCypherText = Convert.FromBase64String(cypherText);
//Problematic line
var bytesPlainTextData = csp.Decrypt(bytesCypherText, false);
plainTextData = System.Text.Encoding.Unicode.GetString(bytesPlainTextData);
return plainTextData;
}
JS
function encrypt(msg, publicKey) {
var jsEncrypt = new JSEncrypt();
jsEncrypt.setPublicKey(publicKey);
var encrypted = jsEncrypt.encrypt(msg);
var base64result = btoa(encrypted);
return base64result;
}
更新/變化:
如果我將密鑰大小The data to be decrypted exceeds the maximum for this modulus of 128 bytes.
1024 而不是 2048,我得到的錯誤是The data to be decrypted exceeds the maximum for this modulus of 128 bytes.
. 根據我在調試器中看到的內容,加密字符串的總字節數為 172。
更新 | 解決方案:
var base64result = btoa(encrypted);
中的這一行 . 直接返回加密值即可。var bytesPlainTextData = csp.Decrypt(bytesCypherText, false);
到var bytesPlainTextData = csp.Decrypt(bytesCypherText, RSAEncryptionPadding.Pkcs1);
.筆記:
您正面臨非對稱加密的限制。 對於大塊數據來說非常慢,並且加密字符串的大小受您使用的 RSA 密鑰大小的限制。
RSA 通常用於交換對稱密鑰和處理大部分數據。 如果您必須對大量數據使用非對稱,那么您需要將有效負載分解為較小的負載並在另一側重建。
RSA 只能將數據加密到最大數量的密鑰大小(2048 位 = 256 字節)減去填充/標頭數據(PKCS#1 v1.5 填充為 11 字節)。
如果如您所說,您只發送 20 個字符,那么確實使用斷點檢查,您的解密函數是否確實獲得了足夠小的密碼文本。 如果不是,您需要回溯並檢查發送錯誤內容的位置。
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