After receiving the request, the server verifies that the received message size is 68 bytes. If it is not, the server either drops the request (if the message size does not equal 48 bytes) or treats it as an unauthenticated request (if the message size is 48 bytes). Assuming that the received message size is 68 bytes, the server extracts the RID from the received message. The server uses it to call the NetrLogonComputeServerDigest method (as specified in [MS-NRPC] section 3.5.4.8.2) to compute the crypto-checksums and select the crypto-checksum based on the most significant bit of the Key Identifier subfield from the received message, as specified in section 3.2.5. The server then sends a response to the client, setting the Key Identifier field to 0 and the Crypto-Checksum field to the computed crypto-checksum.