You can check that the version of GnuPG that you want to install is original and unmodified by either verifying the file's signature or comparing the checksum with the one published in the release announcement.

If you already have a trusted version of GnuPG installed, you can check the supplied signature. For example, to check the signature of the file gnupg-2.2.15.tar.bz2, you can use this command:

$ gpg --verify gnupg-2.2.15.tar.bz2.sig gnupg-2.2.15.tar.bz2

Note: you should never use a GnuPG version you just downloaded to check the integrity of the source — use an existing, trusted GnuPG installation, e.g., the one provided by your distribution.

If the output of the above command is similar to the following, then either you don't have our distribution keys (our signing keys are here) or the signature was generated by someone else and the file should be treated suspiciously.

gpg: Signature made Fri 09 Oct 2015 05:41:55 PM CEST using RSA key ID 4F25E3B6
gpg: Can't check signature: No public key
gpg: Signature made Tue 13 Oct 2015 10:18:01 AM CEST using RSA key ID 33BD3F06
gpg: Can't check signature: No public key

If you instead see:

gpg: Good signature from "Werner Koch (dist sig)" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: D869 2123 C406 5DEA 5E0F  3AB5 249B 39D2 4F25 E3B6
gpg: Signature made Tue 13 Oct 2015 10:18:01 AM CEST using RSA key ID 33BD3F06
gpg: Good signature from "NIIBE Yutaka (GnuPG Release Key) <gniibe@fsij.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 031E C253 6E58 0D8E A286  A9F2 2071 B08A 33BD 3F06

then you have a copy of our keys and the signatures are valid, but either you have not marked the keys as trusted or the keys are a forgery. In this case, at the very least, you should compare the fingerprints that are shown to those on the signing keys page. Even better is to compare the fingerprints with those shown on our business cards, which we handout at events that we attend.

Ideally, you'll see something like:

gpg: Signature made Fri 09 Oct 2015 05:41:55 PM CEST using RSA key ID 4F25E3B6
gpg: Good signature from "Werner Koch (dist sig)" [full]
gpg: Signature made Tue 13 Oct 2015 10:18:01 AM CEST using RSA key ID 33BD3F06
gpg: Good signature from "NIIBE Yutaka (GnuPG Release Key) <gniibe@fsij.org>" [full]

This means that the signature is valid and that you trust this key (either you signed it or someone you trusted did).

If you are not able to use an old version of GnuPG, you can still verify the file's SHA-1 checksum. This is less secure, because if someone modified the files as they were transferred to you, it would not be much more effort to modify the checksums that you see on this webpage. As such, if you use this method, you should compare the checksums with those in release announcement. This is sent to the gnupg-announce mailing list (among others), which is widely mirrored. Don't use the mailing list archive on this website, but find the announcement on several other websites and make sure the checksum is consistent. This makes it more difficult for an attacker to trick you into installing a modified version of the software.

Assuming you downloaded the file gnupg-2.2.15.tar.bz2, you can run the sha1sum command like this:

sha1sum gnupg-2.2.15.tar.bz2

and check that the output matches the SHA-1 checksum reported on this site. An example of a sha1sum output is:

1909afdad3cf29583126c471298da290399270f4  gnupg-2.2.15.tar.bz2

For your convenience, all SHA-1 check-sums available for software that can be downloaded from our site, have been gathered below.

1909afdad3cf29583126c471298da290399270f4  gnupg-2.2.15.tar.bz2
f5f7eeadfdf6ad971b5313f045083b4f95ace07b  gnupg-w32-2.2.15_20190326.exe
5245ce38b198cecd57775fb3c7b7328ec1a2a615  libgpg-error-1.36.tar.bz2
4a8ef9db6922f3a31992aca5640b4198a69b58fc  libgcrypt-1.8.4.tar.bz2
a98385734a0c3f5b713198e8d6e6e4aeb0b76fde  libksba-1.3.5.tar.bz2
6d81bf42fa91ed2894df8b65764ce899e39776f8  libassuan-2.5.3.tar.bz2
05cf57cd8400b338b94bdce7287397c24315ac49  ntbtls-0.1.2.tar.bz2
f9d63e9747b027e4e404fe3c20c73c73719e1731  npth-1.6.tar.bz2
693bdf9f48dfb3e040d92f50b1bb464e268b9fb0  pinentry-1.1.0.tar.bz2
4653b273fd2820ba4d5f382474b3e79a9367beb9  gpgme-1.13.0.tar.bz2
61475989acd12de8b7daacd906200e8b4f519c5a  gpa-0.10.0.tar.bz2
e708d4aa5ce852f4de3f4b58f4e4f221f5e5c690  dirmngr-1.1.1.tar.bz2
a7d5021a6a39dd67942e00a1239e37063edb00f0  gnupg-2.0.31.tar.bz2
13747486ed5ff707f796f34f50f4c3085c3a6875  gnupg-1.4.23.tar.bz2
d4c9962179d36a140be72c34f34e557b56c975b5  gnupg-w32cli-1.4.23.exe