to generate a trusted root certificate, an intermediate certificate, and a server certificate.
We use `certificateAuthority(int)` to create certificates that can sign other certificates. The
int specifies how many intermediate certificates are allowed beneath it in the chain.

```java
HeldCertificate rootCertificate = new HeldCertificate.Builder()
    .certificateAuthority(1)
    .build();

 * `api.publicobject.com` are valid if either A's or B's certificate is in the chain.
 *
 * ## Warning: Certificate Pinning is Dangerous!
 *
 * Pinning certificates limits your server team's abilities to update their TLS certificates. By
 * pinning certificates, you take on additional operational complexity and limit your ability to
 * migrate between certificate authorities. Do not use certificate pinning without the blessing of

     * certificate can sign other certificates (but those certificates cannot themselves sign
     * certificates). Set this to 1 so this certificate can sign intermediate certificates that can
     * themselves sign certificates. Add one for each additional layer of intermediates to permit.
     */
    fun certificateAuthority(maxIntermediateCas: Int) =
      apply {

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.

The process to acquire one of these certificates used to be cumbersome, require quite some paperwork and the certificates were quite expensive.

But then **[Let's Encrypt](https://letsencrypt.org/)** was created.

on-300-000-iranians-using-fake-google-certificate.html). It also assumes your HTTPS servers’ certificates are signed by a certificate authority.

Use [CertificatePinner](https://square.github.io/okhttp/5.x/okhttp/okhttp3/-certificate-pinner/) to restrict which certificates and certificate authorities are trusted. Certificate pinning increases security, but limits your server team’s abilities to update their TLS certificates. **Do not use certificate pinning without the blessing of your server’s...

@file:Suppress("DEPRECATION")

package okhttp3

import java.security.Principal
import java.security.cert.Certificate
import javax.net.ssl.SSLPeerUnverifiedException
import javax.net.ssl.SSLSession
import javax.net.ssl.SSLSessionContext
import javax.security.cert.X509Certificate

class FakeSSLSession(
  vararg val certificates: Certificate,
) : SSLSession {
  override fun getApplicationBufferSize(): Int = throw UnsupportedOperationException()

    // Add a bad intermediate CA and have that issue a rogue certificate for localhost. Prepare
    // an SSL context for an attacking webserver. It includes both these rogue certificates plus the
    // trusted good certificate above. The attack is that by including the good certificate in the
    // chain, we may trick the certificate pinner into accepting the rouge certificate.
    val compromisedIntermediateCa =
      HeldCertificate

  /** Returns a possibly-empty list of certificates that identify this peer. */
  @get:JvmName("localCertificates") val localCertificates: List<Certificate>,
  // Delayed provider of peerCertificates, to allow lazy cleaning.
  peerCertificatesFn: () -> List<Certificate>,
) {
  /** Returns a possibly-empty list of certificates that identify the remote peer. */
  @get:JvmName("peerCertificates")

 * They specify that the call may be plaintext (`http`) or encrypted (`https`), but not which cryptographic algorithms should be used. Nor do they specify how to verify the peer's certificates (the [HostnameVerifier](https://developer.android.com/reference/javax/net/ssl/HostnameVerifier.html)) or which certificates can be trusted (the [SSLSocketFactory](https://developer.android.com/reference/org/apache/http/conn/ssl/SSLSocketFactory.html)).

            |    certificate: ${CertificatePinner.pin(cert)}
            |    DN: ${cert.subjectDN.name}
            |    subjectAltNames: ${OkHostnameVerifier.allSubjectAltNames(cert)}
            """.trimMargin(),
          )
        } else {
          throw SSLPeerUnverifiedException(
            "Hostname ${address.url.host} not verified (no certificates)",
          )
        }
      }