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When signing code with Microsoft's Signtool, there are a couple different options when specifying a timestamp URL, /t and /tr.

/t can specify an Authenticode timestamp URL and /tr is supposed to be used with an RFC 3161 compliant timestamp server.

Is there a way to analyze the timestamp on a file to figure out if /t or /tr was used? If it is Authenticode or RFC 3161?

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Yes. Microsoft's signtool.exe will print a summary of digital signatures on a previously signed file, including which standard was used to create the timestamp, when invoked with the following syntax:

signtool verify /all /pa Filename

To illustrate, subject one of your own files to Symantec's procedure for applying dual signatures. That will result in 2 digital signatures on your file, each with a corresponding timestamp. One timestamp will be applied using Authenticode, and the other with RFC 3161.

Note that Symantec's procedure suggests verifying the result by viewing the Digital Signatures tab of the file's RMB properties . That tab provides the timestamp value (date and time), but not the timestamp standard.

Once you complete the procedure, view the summary of digital signatures with the signtool verify command as suggested above. The timestamp standard will be shown in the "Timestamp" field. For example, here is what you will see if you dual sign a file named MyDigitallySigned.dll:

C:\Users\myusername>signtool verify /all /pa MyDigitallySigned.dll
File: MyDigitallySigned.dll
Index==Algorithm==Timestamp====
========================================
0      sha1       Authenticode
1      sha256     RFC3161
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Implementation details are here: https://msdn.microsoft.com/en-us/library/windows/desktop/bb931395(v=vs.85).aspx

In short, the signing is standardised. The only thing different between /t and /tr should be the protocol used to get the timestamp signature. Signtool does its own thing with the signature in both cases: copies it as a countersignature into the PKCS#7 message that is the authenticode signature.

You might be able to infer the method used by inspecting the signature, if you can map CA certificates to protocols and they are distinct, but there should be no reason to do this.

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