finish post abput gpg public key

content/posts/2023-11-15-using_gpg_public_key.md

@@ -2,24 +2,88 @@
 title = "Using GPG Public Key"
 +++
 
-GNU Privacy Guart (GPG) is an pupular two factor encrytpion system often used for signing or encrypting emails, files or even git commits.
+GNU Privacy Guard (GPG) is an popular two factor encryption system often used for signing or encrypting emails, files or even git commits.
-This post foruces on using provided public key to check signature validity for files signed using complementary public key.
+This post focuses on using provided public key to check signature validity for files signed using complementary public key.
+
+## Install GPG
+On Linux it's found in nearly all distributions with package name of either gpg or gpg2. If both are present and gpg is not an
+alias to gpg2 please use gpg2.
+On Windows besides using WSL there is native GPG distribution named gpg4win.
 
 ## Importing Key
-One way to keep prublic keys is by using a keyserver such as _hkps://keyserver.ubuntu.com_.
+One way to keep public keys is by using a keyserver such as _hkps://keyserver.ubuntu.com_ or _hkp://pgp.mit.edu_.
-To import key with ID **3BDD542C9B0BE180D5802DFF020C42B7A9ABA3E2** from  _hkps://keyserver.ubuntu.com_ keyserver
+To import key with ID _3BDD542C9B0BE180D5802DFF020C42B7A9ABA3E2_ from  **hkps://keyserver.ubuntu.com** keyserver
 issue command:
 ```bash
 $ gpg2 --keyserver hkps://keyserver.ubuntu.com --recv-key 3BDD542C9B0BE180D5802DFF020C42B7A9ABA3E2
 ```
+
+Output of the command above will look like:
+
+```
+gpg: /home/akill/.gnupg/trustdb.gpg: trustdb created
+gpg: key 020C42B7A9ABA3E2: public key "Asmir A (new key 300523) <asmir.abdulahovic@gmail.com>" imported
+gpg: Total number processed: 1
+gpg:               imported: 1
+```
+
 It's also possible to use "short" ID by using only the last 8 digits of hexadecimal
-ID representation, in our case **A9ABA3E2** - but it's discourages because of possible ID collisions.
+ID representation, in our case _A9ABA3E2_ - but it's discouraged because of possible ID collisions.
 
 To search and import a key using email, example _asmir.abdulahovic@gmail.com_ issue command:
 ```bash
-$ gpg2  --keyserver hkps://keyserver.ubuntu.com \
+$ gpg2  --keyserver hkps://keyserver.ubuntu.com --search-keys "asmir.abdulahovic@gmail.com"
-        --search-keys "asmir.abdulahovic@gmail.com"
 ```
 
-Note **hkps** protocol selection acts simmilary as **https** for **http**,
+Note _hkps_ protocol selection acts similarly as _https_ for _http_,
-prefferably use it to avoid **MITM** and other attacks.
+preferably use it to avoid _MITM_ and other attacks.
+
+## Verify Signature
+After successfully importing the public key it's possible to verify signature of a 
+given file by issuing following command:
+```bash
+$ gpg2 --verify my_file.png.asc
+```
+Please notice .asc extension in the command above.
+It's a result of using gpg to attach the signature at the end of the file while both file and signature are
+represented in ASCII format.
+It's, however, possible to compress the file and add signature in binary format.
+In that case it's conventional practise is to use .gpg extension.
+So in previous case file would be named _my_file.png.gpg_.
+Verifying it would be identical to .asc file.
+
+After verifying we still need original file. To extract it use:
+```bash
+$ gpg2 --out my_file.png --decrypt my_file.png.asc
+```
+
+Interestingly for files like .pdf which ignore data appended to the end of the file it's possible to attach
+a signature and use resulting file as normal .pdf while being able to check the same signature.
+More on that in other post.
+
+## Export Key
+
+Simply issue:
+```
+$ gpg2 --export --armor <KEY_ID>
+```
+
+Lastly I'll attach my public key, output of the command above, here which
+can also be found in about/ section of this site.
+
+```
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=nRnt
+-----END PGP PUBLIC KEY BLOCK-----
+```