How to Verify a GPG Signature

A step-by-step guide that helps you figure out if the GPG signature is verified

Last Updated: June 2, 2022

This how-to explains a clear and step-by-step, 1-minute process to verify that a file in your possession was digitally signed by a particular GPG Secret Key and has been unmodified since the time of signing.

Part 1

Part 1 of 2:

Downloading What You Need

To verify your belief that someone has signed a file, you will need a copy of that person's Public Key, a copy of the file, and a copy of the signature-file that was allegedly created through the interaction of the person's Secret Key and the file.

1
Acquire the Public Key.
- Import the Public Key into GPG.
2
Acquire a copy of the file in question.
- Save it in a Folder.
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3
Acquire a copy of the signature-file in question.
- Save it in the same Folder.

Part 2

Part 2 of 2:

Using GPG to Verify that someone's Secret Key Signed the File in Question

GPG will help you verify the relationship between your three files.

1
Open a command-line interface.
- Change the working directory to the Folder where your file and signature-file are saved.
2
Verify the signature.
- Type the following command into a command-line interface:
- gpg --verify [signature-file] [file]
- E.g., if you have acquired
- (1) the Public Key 0x416F061063FEE659,
- (2) the Tor Browser Bundle file (tor-browser.tar.gz), and
- (3) the signature-file posted alongside the Tor Browser Bundle file (tor-browser.tar.gz.asc),
- You would type the following:
- gpg --verify tor-browser.tar.gz.asc tor-browser.tar.gz

Community Q&A

Question

This guide shows how it's done on Windows, how is this done on Linux and macOS? In the same way or is it different?

Radj307

Community Answer

The method is identical for all platform-specific implementations of the GPG utility.
Question

'GPG' is not recognized as an internal or external command, operable program or batch file. What is wrong?

Radj307

Community Answer

You will need GPG installed to be able to use the GPG command. On Windows, you can use GPG4Win.
Question

How can I acquire the Public Key in Part 1 for the file targeted for download?

Radj307

Community Answer

The distributor of the file likely has their PGP public key somewhere on their website.

Warning

Although you are now certain the Secret Key bound to the Public Key you possess was used to sign the file, you must still take precautions to ensure that this Public Key actually belongs to the person you believe it belongs to. Nothing prevents an adversary from making keys that appear to belong to someone.
If you have not imported someone's Public Key to your GPG Keyring, this procedure does not work.
The person may name the signature-file anything they want: the names of the file and the signature-file do not need to be similar or related.