2.4

[[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]]

Verify using OpenPGP (optional)

If you know OpenPGP, you can also verify your download using an OpenPGP signature instead of, or in addition to, our browser extension or BitTorrent.

1. Download and import the [[Tails signing key|tails-signing.key]].

2. Download the OpenPGP signature for the Tails [[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]] USB image OpenPGP signature for the Tails [[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]] ISO image and save it to the same folder where you saved the image.

Basic OpenPGP verification

[[!toggle id="basic-openpgp" text="See instructions for basic OpenPGP verification."]] [[!toggleable id="basic-openpgp" text=""" [[!toggle id="basic-openpgp" text=""]]

This section provides simplified instructions:

• In Windows with Gpg4win
• In macOS with GPGTools
• In Tails
• Using the command line

In Windows with Gpg4win

Download the [[Tails signing key|tails-signing.key]] and import it into Gpg4win.

See the [[Gpg4win documentation on importing keys|https://www.gpg4win.org/doc/en/gpg4win-compendium_15.html]].

See the [[Gpg4win documentation on verifying signatures|http://www.gpg4win.org/doc/en/gpg4win-compendium_24.html#id4]].

Verify that the date of the signature is at most five days earlier than the latest version: [[!inline pages="inc/stable_amd64_date" raw="yes" sort="age"]].

If the following warning appears:

Not enough information to check the signature validity.
Signed on ... by tails@boum.org (Key ID: 0x58ACD84F
The validity of the signature cannot be verified.

Then the image is still correct according to the signing key that you downloaded. To remove this warning you need to authenticate the signing key through the OpenPGP Web of Trust.

In macOS using GPGTools

Download the [[Tails signing key|tails-signing.key]] and import it into GPGTools.

See the [[GPGTools documentation on importing keys|https://gpgtools.tenderapp.com/kb/gpg-keychain-faq/how-to-find-public-keys-of-your-friends-and-import-them#import-key-file]].

1. Open Finder and navigate to the folder where you saved the image and the signature.
2. Control-click on the image and choose Services ▸ OpenPGP: Verify Signature of File.

In Tails

Tails comes with the Tails signing key already imported.

1. Open the file browser and navigate to the folder where you saved the image and the signature.
2. Right-click (on Mac, click with two fingers) on the signature and choose Open With Verify Signature.
3. The verification of the image starts automatically:

   [[!img install/inc/screenshots/verifying_in_tails.png link="no"]]

4. After the verification finishes, you should see a notification that the signature is good:

   [[!img install/inc/screenshots/verifying_in_tails_img_notification.png link="no"]]

   [[!img install/inc/screenshots/verifying_in_tails_iso_notification.png link="no"]]

   Verify that the date of the signature is at most five days earlier than the latest version: [[!inline pages="inc/stable_amd64_date" raw="yes" sort="age"]].

Using the command line

1. Download the [[Tails signing key|tails-signing.key]] and import it into GnuPGP.

   To import the Tails signing key into GnuPGP, open a terminal and navigate to the folder where you saved the Tails signing key.

   Execute:

   gpg --import tails-signing.key

2. In a terminal, navigate to the folder where you saved the image and the signature.

3. Execute:

   [[!inline pages="inc/stable_amd64_img_gpg_verify" raw="yes" sort="age"]]

   [[!inline pages="inc/stable_amd64_iso_gpg_verify" raw="yes" sort="age"]]

   The output of this command should be the following:

   [[!inline pages="inc/stable_amd64_img_gpg_signature_output" raw="yes" sort="age"]]

   [[!inline pages="inc/stable_amd64_iso_gpg_signature_output" raw="yes" sort="age"]]

   Verify that the date of the signature is at most five days earlier than the latest version: [[!inline pages="inc/stable_amd64_date" raw="yes" sort="age"]].

   If the output also includes:

   gpg: WARNING: This key is not certified with a trusted signature!
   gpg: There is no indication that the signature belongs to the owner.
   

   Then the image is still correct according to the signing key that you downloaded. To remove this warning you need to authenticate the signing key through the OpenPGP Web of Trust.

"""]]

Authenticate the signing key through the OpenPGP Web of Trust

Authenticating our signing key through the OpenPGP Web of Trust is the only way that you can be protected in case our website is compromised or if you are a victim of a [[man-in-the-middle attack|doc/about/warning#man-in-the-middle]]. However, it is complicated to do and it might not be possible for everyone because it relies on trust relationships between individuals.

[[!toggle id="web-of-trust" text="Read more about authenticating the Tails signing key through the OpenPGP Web of Trust."]] [[!toggleable id="web-of-trust" text=""" [[!toggle id="web-of-trust" text=""]]

The verification techniques that we present (browser extension, BitTorrent, or OpenPGP verification) all rely on some information being securely downloaded using HTTPS from our website:

• The checksum for the Firefox extension
• The Torrent file for BitTorrent
• The Tails signing key for OpenPGP verification

It is possible that you could download malicious information if our website is compromised or if you are a victim of a man-in-the-middle attack.

OpenPGP verification is the only technique that protects you if our website is compromised or if you are a victim of a man-in-the-middle attack. But, for that you need to authenticate the Tails signing key through the OpenPGP Web of Trust.

One of the inherent problems of standard HTTPS is that the trust put in a website is defined by certificate authorities: a hierarchical and closed set of companies and governmental institutions approved by your web browser vendor. This model of trust has long been criticized and proved several times to be vulnerable to attacks [[as explained on our warning page|doc/about/warning#man-in-the-middle]].

We believe that, instead, users should be given the final say when trusting a website, and that designation of trust should be done on the basis of human interactions.

The OpenPGP [[!wikipedia Web_of_Trust]] is a decentralized trust model based on OpenPGP keys that can help with solving this problem. Let's see this with an example:

1. You are friends with Alice and you really trust her way of making sure that OpenPGP keys actually belong to their owners.
2. Alice met Bob, a Tails developer, in a conference and certified Bob's key as actually belonging to Bob.
3. Bob is a Tails developer who directly owns the Tails signing key. So, Bob has certified the Tails signing key as actually belonging to Tails.

In this scenario, you found, through Alice and Bob, a path to trust the Tails signing key without the need to rely on certificate authorities.

Relying on the Web of Trust requires both caution and intelligent supervision by the users. The technical details are outside of the scope of this document.

Since the Web of Trust is based on actual human relationships and real-life interactions, it is best to get in touch with people knowledgeable about OpenPGP and build trust relationships in order to find your own trust path to the Tails signing key.

For example, you can start by contacting a local [[!wikipedia Linux_User_Group]], [[an organization offering Tails training|support/learn]], or other Tails enthusiasts near you and exchange about their OpenPGP practices.

"""]]