So I am using Android TrustKit to pin certificate’s Subject Public Key Info. One of the security guys suggested I pin modulus of the public key, however, I cannot find any sort of examples on how to do that. Here is my current Android code:

OkHttpClient.Builder()
   .apply {
      authenticator?.let(::authenticator)
      interceptor?.let(::addInterceptor)
      if (config.certificatePin) {
         sslSocketFactory(TrustKit.getInstance().getSSLSocketFactory(serverHostname),
                        TrustKit.getInstance().getTrustManager(serverHostname))
      }
   }
...

I also know how to obtain modulus of the certificate with openssl x509 command in command line. But I can’t figure out how do I pin that data inside the android application. Any ideas or code samples would be appreciated.