using System.Security.Cryptography;
public static void Main()
string keyPem = @"-----BEGIN RSA PRIVATE KEY-----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==
-----END RSA PRIVATE KEY-----";
string ciphertextFromNodeJS = "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";
string ciphertextFromPython = "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";
byte[] numArray = Convert.FromBase64String(ciphertextFromNodeJS);
string str = string.Empty;
using (RSACryptoServiceProvider privateKey = new RSACryptoServiceProvider())
privateKey.ImportFromPem(keyPem);
numArray1 = privateKey.Decrypt(numArray, false);
str = Encoding.UTF8.GetString(numArray1);