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Asked: 2026-05-31T06:48:14+00:00

I’m building an application which is Client (C#) & Server (PHP) based application. I

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I’m building an application which is Client (C#) & Server (PHP) based application.

I want to sign the data on Server using RSA-SHA1 and send to client.

On Server i.e. PHP I’ using PHPSecLib, signing with Private Key.
On client i.e. C# I’m using RSACryptoServiceProvider.
Sign Hash from Server is not matching with the client. I’m providing both C# and PHP Codes:

PHP #Output

BLkgXU6t6IYNdlrgTaJgaGzZtSc9NjY9q67PbidGo0e79SyQ7b18uKSg1a215r583atzIlFYkAyxDCjvQJIBATdeOKpWuzdtRkZqDX7TQAw5jLHdsFjL3lQWABERFUdEs9XuCykb3I8UNVT2UgmMRZ3pyKknCMdc5AlE9mKXOYI=

PHP Code

$plaintext = 'O';
$rsa = new Crypt_RSA();
$rsa->loadKey("<RSAKeyValue><Modulus>3BqiIB3ouyXHDMpW43TlZrx8fkts2FVVARJKNXFRQ/WIlsthDzL2jY2KEJVN6BKE4A51X+8LMzAI+2z3vIgAQT3bRSfOwygpGBjdhhnXJwFlQ6Gf/+z0ffQfVx/DHw3+QWphcwGDBst+KIA6u6ayy+RDE+jEityyyWDiWqkR9J8=</Modulus><Exponent>AQAB</Exponent><P>8a8nuVhIANh7J2TLn4wWTXhZY1tvlyFKaslOeAOVr+wgEWLQpLZ0Jpjm8aUyyOYPXlk7xrA5BOebtz41diu4RQ==</P><Q>6SQ9y3sEMjrf/c4bHGVlhOj4LUVykradWWUNC0ya7llnR8y1djJ1uUut+EoAa1JQCGukuv4K8NvN1Ieo72Fhkw==</Q><DP>cg0VMusNN5DxNRrk2IrUL4TesfuBQpGMO6554DrY1acZTvsRuNj9IQXA3kH2IEYo9H4prk6U6dKeci/iLLze/Q==</DP><DQ>m/pZNXeZ+RkWnrFzxe24m9FZqMAbxThT0Wkf7v1Tcj9yL8EvbmKYDF4riD/KRAMP9HJABbLNExObg6M3TOAz7Q==</DQ><InverseQ>w8PvW8srrPCuOcphBKXSyoZxCZn81+rovBxuE8AB95m5X+URE8SunK7f+g7hBBin6nUOaVGohBP8jzkQEsdx1Q==</InverseQ>  <D>AsVPDypxOJHkLJQLffeFv8JVqt1WNG72j/nj90JC7KEVpBhRU3inw+ZpO4Y1odtB0vQ7pAaFVJKhOlEH2Va48hNUEQujML8rE+LZXgI3lu0TlqOCIqTHIljeJry0ca30XFtFDp9kh0Kr/0CgGMqgIed+hDUjAad8ke9D2YicDok=</D></RSAKeyValue>",2);//2 for Pivate Key XML
$signature = $rsa->sign($plaintext); 
echo base64_encode($signature);

C# Output 

aCqhRe/lj99Yv0cLVxZD9v0M29qiEhlNOTIGuVuUbw58sp/9lLQEoMqKQrIfyTA7O2OIw5QWV9eZXlAlOlvvBPR1IOahk3mr8N8xaT5+T2fG5cEldeOWwKKxSNHqEBzIVT/4FQqlpvrmtoHJIL6n6KjDb/HQD2kgmMLmQffVYGo=

C# Code

string private_xml = @"<RSAKeyValue><Modulus>3BqiIB3ouyXHDMpW43TlZrx8fkts2FVVARJKNXFRQ/WIlsthDzL2jY2KEJVN6BKE4A51X+8LMzAI+2z3vIgAQT3bRSfOwygpGBjdhhnXJwFlQ6Gf/+z0ffQfVx/DHw3+QWphcwGDBst+KIA6u6ayy+RDE+jEityyyWDiWqkR9J8=</Modulus><Exponent>AQAB</Exponent><P>8a8nuVhIANh7J2TLn4wWTXhZY1tvlyFKaslOeAOVr+wgEWLQpLZ0Jpjm8aUyyOYPXlk7xrA5BOebtz41diu4RQ==</P><Q>6SQ9y3sEMjrf/c4bHGVlhOj4LUVykradWWUNC0ya7llnR8y1djJ1uUut+EoAa1JQCGukuv4K8NvN1Ieo72Fhkw==</Q><DP>cg0VMusNN5DxNRrk2IrUL4TesfuBQpGMO6554DrY1acZTvsRuNj9IQXA3kH2IEYo9H4prk6U6dKeci/iLLze/Q==</DP><DQ>m/pZNXeZ+RkWnrFzxe24m9FZqMAbxThT0Wkf7v1Tcj9yL8EvbmKYDF4riD/KRAMP9HJABbLNExObg6M3TOAz7Q==</DQ><InverseQ>w8PvW8srrPCuOcphBKXSyoZxCZn81+rovBxuE8AB95m5X+URE8SunK7f+g7hBBin6nUOaVGohBP8jzkQEsdx1Q==</InverseQ>  <D>AsVPDypxOJHkLJQLffeFv8JVqt1WNG72j/nj90JC7KEVpBhRU3inw+ZpO4Y1odtB0vQ7pAaFVJKhOlEH2Va48hNUEQujML8rE+LZXgI3lu0TlqOCIqTHIljeJry0ca30XFtFDp9kh0Kr/0CgGMqgIed+hDUjAad8ke9D2YicDok=</D></RSAKeyValue>";


            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(private_xml);
            string Text = "O";
            byte[] Data = Encoding.ASCII.GetBytes(Text);

            byte[] signature = rsa.SignData(Data, new SHA1CryptoServiceProvider());
            string o = Convert.ToBase64String(signature);
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1 Answer

  1. Editorial Team

    It seems there is something wrong with SignData Compatablity of PhpSecLib & C# RSA
    Please do visit http://www.dustinhorne.com/post/Asymmetric-Encryption-and-Signing-with-RSA-in-Silverlight.aspx

    I used this to decypt at client i.e. Public Decrypt and PHPSecLib for private Encyption.

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