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-2.2.1.tar.bz2, you can use this command:

$ gpg --verify gnupg-2.2.1.tar.bz2.sig gnupg-2.2.1.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-2.2.1.tar.bz2, you can run the sha1sum command like this:

sha1sum gnupg-2.2.1.tar.bz2

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

5455373fd7208b787f319027de2464721cdd4413  gnupg-2.2.1.tar.bz2

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

5455373fd7208b787f319027de2464721cdd4413  gnupg-2.2.1.tar.bz2
bcf1905655e52e2eec794bcbba72485f7b9ed2d3  gnupg-w32-2.2.1_20170919.exe
a428758999ff573e62d06892e3d2c0b0f335787c  libgpg-error-1.27.tar.bz2
dd35f00da45602afe81e01f4d60c40bbdd826fe6  libgcrypt-1.8.1.tar.bz2
a98385734a0c3f5b713198e8d6e6e4aeb0b76fde  libksba-1.3.5.tar.bz2
27391cf4a820b5350ea789c30661830c9a271518  libassuan-2.4.3.tar.bz2
05cf57cd8400b338b94bdce7287397c24315ac49  ntbtls-0.1.2.tar.bz2
93ddf1a3bdbca00fb4cf811498094ca61bbb8ee1  npth-1.5.tar.bz2
85d9ac81ebad3fb082514c505c90c39a0456f1f6  pinentry-1.0.0.tar.bz2
870719cd3d2ef6a7fcb1d6af9ce5446edba7bfc3  gpgme-1.9.0.tar.bz2
c629348725c1bf5dafd57f8a70187dc89815ce60  gpa-0.9.10.tar.bz2
e708d4aa5ce852f4de3f4b58f4e4f221f5e5c690  dirmngr-1.1.1.tar.bz2
a9f024588c356a55e2fd413574bfb55b2e18794a  gnupg-2.0.30.tar.bz2
4bad84fba712626cbbd5adf20988788028c5a5a6  gnupg-1.4.22.tar.bz2
27b8069872d6d2b271222ffb9322dbd6197b0b89  gnupg-w32cli-1.4.22.exe