diff --git a/src/steamnetworkingsockets/steamnetworkingsockets_certs.cpp b/src/steamnetworkingsockets/steamnetworkingsockets_certs.cpp
index f4feec0..596596f 100644
--- a/src/steamnetworkingsockets/steamnetworkingsockets_certs.cpp
+++ b/src/steamnetworkingsockets/steamnetworkingsockets_certs.cpp
@@ -9,19 +9,28 @@
 
 namespace SteamNetworkingSocketsLib {
 
+uint64 CalculatePublicKeyID_Ed25519( const void *pPubKey, size_t cbPubKey )
+{
+	if ( cbPubKey != 32 )
+		return 0;
+
+	SHA256Digest_t digest;
+	CCrypto::GenerateSHA256Digest( pPubKey, cbPubKey, &digest );
+
+	// First 8 bytes
+	return LittleQWord( *(uint64*)&digest );
+}
+
 uint64 CalculatePublicKeyID( const CECSigningPublicKey &pubKey )
 {
 	if ( !pubKey.IsValid() )
 		return 0;
 
 	// SHA over the whole public key.
-	SHA256Digest_t digest;
 	uint8 data[32];
-	DbgVerify( pubKey.GetRawData( data ) == sizeof(data) );
-	CCrypto::GenerateSHA256Digest( data, sizeof(data), &digest );
-
-	// First 8 bytes
-	return LittleQWord( *(uint64*)&digest );
+	uint32 cbPubKey = pubKey.GetRawData( data );
+	Assert( cbPubKey == sizeof(data) );
+	return CalculatePublicKeyID_Ed25519( data, cbPubKey );
 }
 
 // Returns:
diff --git a/src/steamnetworkingsockets/steamnetworkingsockets_certstore.cpp b/src/steamnetworkingsockets/steamnetworkingsockets_certstore.cpp
index 3671439..16c8952 100644
--- a/src/steamnetworkingsockets/steamnetworkingsockets_certstore.cpp
+++ b/src/steamnetworkingsockets/steamnetworkingsockets_certstore.cpp
@@ -244,7 +244,7 @@ struct PublicKey
 		if ( m_eTrust >= k_ETrust_Trusted )
 			return true;
 		Assert( m_eTrust <= k_ETrust_NotTrusted );
-		Assert( !m_status_msg.empty() ); // We should nkow the reason for any key we don't trust
+		Assert( !m_status_msg.empty() ); // We should know the reason for any key we don't trust
 		return false;
 	}
 
@@ -666,6 +666,38 @@ const CertAuthScope *CertStore_CheckCert( const CMsgSteamDatagramCertificateSign
 		return nullptr;
 	}
 
+	// Check if their key has specifically been revoked.
+	if ( outMsgCert.key_type() != CMsgSteamDatagramCertificate_EKeyType_ED25519 )
+	{
+		V_sprintf_safe( errMsg, "Cert has invalid key type %d", (int)outMsgCert.key_type() );
+		return nullptr;
+	}
+	uint64 nKeyID = CalculatePublicKeyID_Ed25519( outMsgCert.key_data().c_str(), outMsgCert.key_data().length() );
+	if ( nKeyID == 0)
+	{
+		V_sprintf_safe( errMsg, "Cert has invalid public key" );
+		return nullptr;
+	}
+	const PublicKey *pPubKey = FindPublicKey( nKeyID );
+	if ( pPubKey )
+	{
+		if ( pPubKey->m_eTrust == k_ETrust_NotTrusted )
+		{
+			// Hm - this status doesn't mean "bad", it just means that the cert in the cert store
+			// with this key was not able to be verified.  This is an an unusual situation, ordinarily
+			// we should not have any certs in the cert store that we are not able to trust.  Still, we
+			// just specific ally verified trust above.  So let's continue on, but without adding this
+			// to the cert store.
+		}
+		else if ( !pPubKey->IsTrusted() )
+		{
+			// Key is revoked.
+			Assert( pPubKey->m_eTrust == k_ETrust_Revoked );
+			V_sprintf_safe( errMsg, "Cert has untrusted public key.  %s", pPubKey->m_status_msg.c_str() );
+			return nullptr;
+		}
+	}
+
 	return pResult;
 }
 
@@ -677,7 +709,7 @@ bool CheckCertAppID( const CMsgSteamDatagramCertificate &msgCert, const CertAuth
 	{
 		if ( !pCACertAuthScope || pCACertAuthScope->m_apps.HasItem( nAppID ) )
 			return true;
-		V_sprintf_safe( errMsg, "Cert is not restricted by appid, by CA trust chain is, and does not authorize %u", nAppID );
+		V_sprintf_safe( errMsg, "Cert is not restricted by appid, but CA trust chain is, and does not authorize %u", nAppID );
 		return true;
 	}
 
@@ -713,7 +745,7 @@ bool CheckCertPOPID( const CMsgSteamDatagramCertificate &msgCert, const CertAuth
 	{
 		if ( !pCACertAuthScope || pCACertAuthScope->m_pops.HasItem( popID ) )
 			return true;
-		V_sprintf_safe( errMsg, "Cert is not restricted by POPID, by CA trust chain is, and does not authorize %s", SteamNetworkingPOPIDRender( popID ).c_str() );
+		V_sprintf_safe( errMsg, "Cert is not restricted by POPID, but CA trust chain is, and does not authorize %s", SteamNetworkingPOPIDRender( popID ).c_str() );
 		return true;
 	}
 
diff --git a/src/steamnetworkingsockets/steamnetworkingsockets_internal.h b/src/steamnetworkingsockets/steamnetworkingsockets_internal.h
index 3989cd0..7bc7b98 100644
--- a/src/steamnetworkingsockets/steamnetworkingsockets_internal.h
+++ b/src/steamnetworkingsockets/steamnetworkingsockets_internal.h
@@ -442,6 +442,7 @@ extern uint32 Murmorhash32( const void *data, size_t len );
 /// although not really cryptographically secure.  (We are in charge of the
 /// set of public keys and we expect it to be reasonably small.)
 extern uint64 CalculatePublicKeyID( const CECSigningPublicKey &pubKey );
+extern uint64 CalculatePublicKeyID_Ed25519( const void *pPubKey, size_t cbPubKey );
 
 /// Check an arbitrary signature using the specified public key.  (It's assumed that you have
 /// already verified that this public key is from somebody you trust.)