Public i Private Keys (Gpg_pgp Basics)

GPG/PGP Basics

GPG/PGP BasicsUsing gpg for encryption, understanding the basic use of GPG for new users.

Recently someone asked me for a GPG or PGP public key so that they could send some sensitive material to me by email. I understood what they meant, but inwardly I groaned because I've just never had any reason to use public key encryption, and had no idea how to create the key or decrypt what would be sent back to me. Looking at "man bgp" on my Linux box didn't make me feel any better, and a Google search for gpg docs didn't immediately turn up anything that wasn't techno gobbledy-dee-geek. Eventually (after I had figured out the basics by trial and error), I did find GNU Privacy Guard HandBook, which probably would have gotten me up to speed a little faster, but which still was more than I needed to know at the moment. This, therefore, is a quick introduction so that you don't have to get a headache from the man page as I did. After learning what is presented here, you can visit the GNU page for more in depth coverage.Public key, private keyThe basic concept is this: You generate a pair of matched keys. One of these is referred to as your "Public" key, and the other as "Private". You give the Public key to anyone who asks for it; you can even publish it on your web site. You keep your Private key secret, locked up on your own computer. A document (a text or binary file) can be encrypted using either key, and is decrypted with the other. The choice of which key to use to encrypt depends upon your purpose.For example, if you want to send me something, you'd encrypt it using my public key. No one else can decrypt it; only my private key will work. On the other hand, I might be concerned that it really is you sending me a message. In that case, you'd encrypt your message using your private key (this is called "signing"). If I can decrypt it with your public key (presumably I somehow obtained that key and trust that it really is yours), I know that the message really came from you.An exampleYou can test this all out on one computer using two (or more) user accounts. I'm going to assume that user "tom" wants to send an encrypted message to user "marge". The first thing Marge needs to do is generate her keys:[marge@apl marge]$ gpg --gen-keygpg (GnuPG) 1.0.6; Copyright (C) 2001 Free Software Foundation, Inc.This program comes with ABSOLUTELY NO WARRANTY.This is free software, and you are welcome to redistribute itunder certain conditions. See the file COPYING for details.

gpg: Warning: using insecure memory!gpg: /home/marge/.gnupg: directory createdgpg: /home/marge/.gnupg/options: new options file createdgpg: you have to start GnuPG again, so it can read the new options file Because Marge has never created a key before, gpg just creates what it needs and tells her to run it again:[marge@apl marge]$ gpg --gen-keygpg (GnuPG) 1.0.6; Copyright (C) 2001 Free Software Foundation, Inc.This program comes with ABSOLUTELY NO WARRANTY.This is free software, and you are welcome to redistribute itunder certain conditions. See the file COPYING for details.

gpg: Warning: using insecure memory!gpg: /home/marge/.gnupg/secring.gpg: keyring createdgpg: /home/marge/.gnupg/pubring.gpg: keyring createdPlease select what kind of key you want: (1) DSA and ElGamal (default) (2) DSA (sign only) (4) ElGamal (sign and encrypt)Your selection? 1 DSA keypair will have 1024 bits.About to generate a new ELG-E keypair. minimum keysize is 768 bits default keysize is 1024 bits highest suggested keysize is 2048 bitsWhat keysize do you want? (1024) Requested keysize is 1024 bitsPlease specify how long the key should be valid. 0 = key does not expire = key expires in n days w = key expires in n weeks m = key expires in n months y = key expires in n yearsKey is valid for? (0) Key does not expire at allIs this correct (y/n)? y You need a User-ID to identify your key; the software constructs the user idfrom Real Name, Comment and Email Address in this form: "Heinrich Heine (Der Dichter) "

Real name: MargeEmail address: [email protected]: Marge's GPG key pairYou selected this USER-ID:"Marge (Marge's GPG key pair) "

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? OYou need a Passphrase to protect your secret key.

Enter passphrase: Sbr6wh wscartBM, iscaa2dRepeat passphrase: Sbr6wh wscartBM, iscaa2dWe need to generate a lot of random bytes. It is a good idea to performsome other action (type on the keyboard, move the mouse, utilize thedisks) during the prime generation; this gives the random numbergenerator a better chance to gain enough entropy..+++++++++++++++++++++++++.+++++++++++++++..+++++++++++++++++++++++++++++++++++....++++++++++.++++++++++++++++++++++++++++++.+++++.++++++++++>++++++++++>++++++++++public and secret key created and signed. (See Random Numbers also)The passphrase entered should be a tough password. It can contain spaces, there's no limit on its length, but of course you will need to remember it. I use mnemonic aids to generate passwords and passphrases. For example, the passphrase above comes from this:She'll be riding six white horses when she comes around that Big Mountain, if she comes at all today

Fairly easy for me to remember, but a good, tough passphrase.If you are working on a single-user machine, you probably will need to switch away and generate some activity to get the keys created. Once that's done, Marge can list her keys:[marge@apl marge]$ gpg --list-keysgpg: Warning: using insecure memory!/home/marge/.gnupg/pubring.gpg------------------------------pub 1024D/FBE5BA2A 2001-11-17 Marge (Marge's GPG key pair) sub 1024g/78681206 2001-11-17 Now she's ready to create the public key that she will send to Tom. We assume for the moment that she has a perfectly secure way of getting it to Tom so that Tom really knows it came from her; for example, she physically hands him a CD which has the key on it. She could also publish it on her web page (there's more information about how to do that securely at the GNU Privacy Guard page referenced above) or (more likely), she just emails to him (she could also use a Public Key Server; see the GNU page for more on that). Email is not completely unreasonable: it doesn't matter if someone else intercepts and reads that email, because all it contains is the public key. That key is only useful for sending documents that Marge (and only Marge) can decrypt; stealing it does not let you impersonate Marge. What Tom has to be concerned about is someone forging email that pretends to be from Marge but that actually contains a forged public key: if Tom used that to encrypt his data, and the forger could intercept that transmission also, the forger could decrypt the data (and of course Marge could not!). So what Tom probably should do (if he's really worried about this) is call Marge on the telephone and ask her to read some of her key.Here Marge prepares her public key:[marge@apl marge]$ gpg --armor --export [email protected] > mypkgpg: Warning: using insecure memory![marge@apl marge]$ cat mypk-----BEGIN PGP PUBLIC KEY BLOCK-----Version: GnuPG v1.0.6 (GNU/Linux)Comment: For info see http://www.gnupg.org

mQGiBDv2vMARBACPHwe3BXmJXF5dvXxGEuxYIbYoY2naOmaArFsv1Pgl3GqhhAP7GTGvN4A4Xo80S8i8mrSsseHE/RD7F2PS045dzP/LbDcI7EqnfU2BDoIfEmTsTuplBKjOJUh7luhFbj2gdpbmmTUD/1BBKd42pIk/GPUcynMS9TG4kUyB6UdtRF7NydYPo4T+0fIY8mbh5VRigoVVsukX8xuI+QaS5iB/D4j36+zk/iRy171dY43OuwCgm6rQa8vmmGDyCCUWFX0PVlQn5MMf97GadIAGgh1pdD7bMfB4FI84TyhNHuBDTCn0Ysffnot_a_public_key_but_other_than_this_line_it_looks_like_this_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-----END PGP PUBLIC KEY BLOCK-----[marge@apl marge]$ Using Marge's Public KeyTo use Marge's public key, Tom first has to "import" it. Tom already has his own keys created:[tom@apl tom]$ gpg --list-keysgpg: Warning: using insecure memory!/home/tom/.gnupg/pubring.gpg----------------------------pub 1024D/16B478D3 2001-11-17 Tommy (Tommy Boy) sub 1024g/1E5CDE3C 2001-11-17 To add Marges public key, Tom does this (he's saved the file as "margepk"):[tom@apl tom]$ gpg --import margepkgpg: Warning: using insecure memory!gpg: key FBE5BA2A: public key importedgpg: /home/tom/.gnupg/trustdb.gpg: trustdb createdgpg: Total number processed: 1gpg: imported: 1 Now when he lists keys, he has Marge's:[tom@apl tom]$ gpg --list-keysgpg: Warning: using insecure memory!/home/tom/.gnupg/pubring.gpg----------------------------pub 1024D/16B478D3 2001-11-17 Tommy (Tommy Boy) sub 1024g/1E5CDE3C 2001-11-17

pub 1024D/FBE5BA2A 2001-11-17 Marge (Marge's GPG key pair) sub 1024g/78681206 2001-11-17 Tom has done all that he really needs to do. The next step is recommended but not strictly necessary:

[tom@apl tom]$ gpg --edit-key [email protected] (GnuPG) 1.0.6; Copyright (C) 2001 Free Software Foundation, Inc.This program comes with ABSOLUTELY NO WARRANTY.This is free software, and you are welcome to redistribute itunder certain conditions. See the file COPYING for details.

gpg: Warning: using insecure memory!

pub 1024D/FBE5BA2A created: 2001-11-17 expires: never trust: -/qsub 1024g/78681206 created: 2001-11-17 expires: never (1). Marge (Marge's GPG key pair)

Command> fpr pub 1024D/FBE5BA2A 2001-11-17 Marge (Marge's GPG key pair) Fingerprint: C294 A900 C769 2AEF C951 2434 0CA6 3EED FBE5 BA2A

Command> sign pub 1024D/FBE5BA2A created: 2001-11-17 expires: never trust: -/q Fingerprint: C294 A900 C769 2AEF C951 2434 0CA6 3EED FBE5 BA2A

Marge (Marge's GPG key pair)

Are you really sure that you want to sign this keywith your key: "Tommy (Tommy Boy) "

Really sign? y You need a passphrase to unlock the secret key foruser: "Tommy (Tommy Boy) "1024-bit DSA key, ID 16B478D3, created 2001-11-17

Enter passphrase: (Tom enters his passphrase here)Command> quit Save changes? y What Tom did was add Marge to his "trusted" keys- keys that he is sure came from who they were supposed to. As I said, it's not absolutely necessary, and you can read more about it at the GNU Privacy Guard Page.Now Tom is ready to encrypt his data:[tom@apl tom]$ gpg --out secrets_to_marge --encrypt secretsgpg: Warning: using insecure memory!You did not specify a user ID. (you may use "-r")

Enter the user ID: [email protected][tom@apl tom]$ ls -l sec*-rw-r--r-- 1 root root 5940 Nov 17 15:21 secrets-rw-rw-r-- 1 tom tom 2738 Nov 17 15:22 secrets_to_marge[tom@apl tom]$ Tom can now send "secrets_to_marge" with safety: only Marge can decrypt the data.When Marge gets it, she'll decrypt it like this:[marge@apl marge]$ gpg --output secrets_from_tom --decrypt secrets_to_margegpg: Warning: using insecure memory!

You need a passphrase to unlock the secret key foruser: "Marge (Marge's GPG key pair) "1024-bit ELG-E key, ID 78681206, created 2001-11-17 (main key ID FBE5BA2A)

Enter passphrase: Sbr6wh wscartBM, iscaa2dgpg: encrypted with 1024-bit ELG-E key, ID 78681206, created 2001-11-17 "Marge (Marge's GPG key pair) "[marge@apl marge]$ ls -l sec*-rw-rw-r-- 1 marge marge 5940 Nov 17 16:09 secrets_from_tom-rw-rw-r-- 1 marge marge 2738 Nov 17 16:09 secrets_to_marge[marge@apl marge]$ That's it. GPG is actually pretty simple, and nothing to get a headache over. Please do read the GNU Privacy Guard HandBook for a far more complete treatment of this subject.See OS X file encryption for gpg on Mac OS X.

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Apparently, Alice and Bob are names commonly used for this sort of article. I didn't know that when I wrote it. See http://catb.org/~esr/jargon/html/A/Alice-and-Bob.html and http://www.conceptlabs.co.uk/alicebob.html

--TonyLawrence

______________________________

This page is a nice short howto for using GNUPG. I feel, however, that some points need clarification, as it is sensitive/personal data that are being dealt with here:

1. The part about publishing one's public key contains a rather misleading and potentially dangerous passage, as it may create a false sense of security:

"Email is not completely unreasonable: it doesn't matter if someone else intercepts and reads that email, because all it contains is the public key. That key is only useful for sending documents that Marge (and only Marge) can decrypt; stealing it does not let you impersonate Marge." This is not entirely true; there's always the possibility of a "Man-in-the-Middle" Attack. Have a look at http://www.glump.net/content/gpg_intro/html/3_Creating_Your_Personal.html#foot311 to see what I mean. Of course, this might be viewed as paranoia, but it's still a consideration, for users who want to take no chances.

[ I guess that's what is meant, in the passage immediately after the one above: "What Tom has to be concerned about is someone forging email that pretends to be from Marge but that actually contains a forged public key: if Tom used that to encrypt his data, and the forger could intercept that transmission also, the forger could decrypt the data (and of course Marge could not!)." but it's not clear enough, IMHO -- the explanation should be more detailed, as in the link above. ]

Also, the guide at http://www.glump.net/content/gpg_intro/ (the above URL), which is entitled "A Practical Introduction to GNU Privacy Guard in Windows", is an excellent geekspeak-free guide for GPG, not only for MS-Windows.

2. The passage:

"So what Tom probably should do (if he's really worried about this) is call Marge on the telephone and ask her to read some of her key." describes a practice that's neither easy, nor the commonly employed; it would be much better if the key's *fingerprint* would be verified by both of the parties. This is the easiest and safest way of verifying keys which were obtained via an insecure means.

3. The part between:

"Tom has done all that he really needs to do. The next step is recommended but not strictly necessary:" and "What Tom did was add Marge to his 'trusted' keys- keys that he is sure came from who they were supposed to." is not correct. A user signs a public key, to show *others* that s/he trusts it (add an extra bit of validity to that key); this possibly also involves the participation in a *web of trust* -- see http://www.gnupg.org/gph/en/manual.html#AEN533 . In order to show *him/herself* s/he trusts a key (so s/he will be able to use it with GPG without any security prompts), one has to set the trust level on this key. See http://www.glump.net/content/gpg_intro/html/4_Encrypting_Decrypting_Fil.html#SECTION00530000000000000000 (4.3.1 Importing the key).

--Doryforos (visitor)

Sat Dec 10 01:09:08 2005: 1423 anonymous

Awesome short summary. Just enough for me to remember how to use it. Thank you for post it!

Tue Feb 14 20:07:24 2006: 1641 anonymous

Short and precise composition of GPG/PGP files.Wonderful!

Wed Mar 15 20:50:39 2006: 1794 anonymous

Thanks, followed the steps and was immediately productive. Thanks!

Fri Jun 16 21:05:13 2006: 2124 CBZ

Very nice. Thank-you!

Mon Nov 20 08:58:00 2006: 2632 vidyasagarcognizantcom

Nice. I was trying some thing more and i got stuck. What i did was i created the public keys and exported it to a file(ex. pkeys.asc). I wanted gpg to use this keyring and not to use the default key ring. I used gpg --armor --batch --encrypt --keyring pkeys.asc --no-default-keyring --recipient user5 1.txt and i am getting errors. It says, gpg: user5: skipped: public key not found gpg: 1.txt: encryption failed: public key not found

But when i list the keys it is showing the keys in its default keyring. If any one knows how to do this please say to me. I am not getting help for this anywhere

Wed Jul 4 16:59:30 2007: 3052 anonymous

This tutorial is among the finest there are in the UNIX/Linux world. The combination of readability and accuracy is perfect. I got my key generated and started encrypting/decrypting in 10 minutes. Some day all of the useless MAN pages will be tossed in favor of material like this. Mr. or Ms. Lawrence, we salute you.

Wed Feb 20 02:44:35 2008: 3679 anonymous

In the "Public Key,Private Key" of your article, you say ...

"In that case, you'd encrypt your message using your private key (this is called "signing")."

No. A signature is a computed summary binary string that uniquely identifies the sender's key, and the content of the email, by creating a validity sum. Usually a sign for a message is only a few 72-char lines long, and it is usually placed in a block near the end of the email. I'm sure that you can edit this article, and put a non-technical explanation of "signing" that is just as correct as what I suggested in my comment.

The only other correction that I would suggest is to explain that you cannot swap your keypair around, making key one public at will, and making the other key private, and then encrypt with the private key. The public key is always the one that you make public, and the private key is always the one that you keep private.

In fact, if you don't get the public key for the person receiving the email, then you cannot encrypt an email to them. This is also true for the person sending email to you - if they don't have your public key, then they can't send you encrypted email.

How do you exchange public keys? Either directly, sending them to each other... or by putting your public key on a "keyserver". You could write another article about keyservers, or you could quickly describe it as a bulletin board on the internet where lots of people put their public keys.

While your article is very good, there are a couple of points that you really "glossed over" at a very high level... so much so that your story of encrypting with your private key and the receiver decrypting with a public key is in error.

Peace, and good will.

Wed Feb 20 03:14:02 2008: 3680 TonyLawrence

Peace to you also, but I have to disagree. The point of signing is as I explained: to prove that the message in fact came from you.

I did not suggest that you "swap keys around" - the point of that section is that I'd use YOUR public key to send you something that I want only you to be able to decript, but you'd use your private key in the "signing" situation.

Wed Feb 20 14:35:08 2008: 3681 TonyLawrence

By the way:

The reason I wrote this page was because I found other web resources confusing. That doesn't mean that they aren't well written: they probably are for a person at a certain level of knowledge and understanding.

That's the thing, really: we all come at things from different starting points. For some people my post here is too basic, for others it is way over their heads. For some, apparently, it's right on the mark.

That's why I encourage people to leave comments or to even submit a whole new article explaining things from *your* perspective ( see http://aplawrence.com/publish.html for more on that). How *you* explain something may be exactly what someone else needs.

Sun Mar 9 03:14:09 2008: 3821 JonR

This is the first time I've understood clearly how GPG basically works. I use it to encrypt my own files, but I've never had to use it to communicate, and would have been at a loss. Now I know how to do that. Regardless of whether some points are debatable, the main ideas behind GPG come through and for average users I think that finding this page will be a memorable event. Thanks very much.

Sun Mar 9 11:49:28 2008: 3823 TonyLawrence

Thank you, Jon and I'm glad it helped you. That's what it's all about - getting our heads pointed in the right direction.

Wed Mar 26 20:56:08 2008: 3904 Arjay

Thanks for an easy to understand article! This is all I needed to use gpg.

Mon Jul 7 19:53:22 2008: 4396 anonymous

In addition to the Alice & Bob names, Eve is also used when speaking about "mitm", or man-in-the-middle. You almost got into this topic when you mentioned someone sending Tom a false public key, pretending to be Marge. Eve, as the eavesdropper, would send Tom a false public key. Tom would encrypt using this false key, Eve would intercept the message, de-crypt it with her private key from the pair that she gave to Tom, and then possibly modify the message and encrypt it with Marge's real public key, and send it along to Marge, assuming Eve could trick Marge as she tricked Tom. Eve is the "(wo)man in the middle" of the conversation.

Mon Jul 7 20:20:40 2008: 4397 JonR

I happen to have been reading a couple of books recently that deal directly or indirectly with cryptography, and as a result my mind keeps coming back to the one absolutely unbreakable crypto method: the one-time pad. If only that system could be made practical, there would be absolute security, subject to the limitation of identity fraud. Even a quantum computer could not break a message encrypted with a one-time pad. The big difficulty, and what makes it impractical to use the method on anything but a very small scale, is getting the page(s) containing the key to the recipient. It sends the users right back to square one.

Tue Sep 22 15:55:33 2009: 6953 Jai http://gazolinia.blogspot.com

Very cool and simple explanation of GPG .

Tue Nov 10 22:27:07 2009: 7517 Jayakumar

Really simple to understand in a single page!!! Nice one.

Thu Nov 12 11:15:02 2009: 7532 senthil

really goood

Thu Nov 26 15:00:22 2009: 7632 Merovance

Thank you. Your article fit me to a T. I appreciate you taking the time to help newbies.

Thu Nov 26 15:10:03 2009: 7633 TonyLawrence

Thank you for taking the time to leave a comment. We appreciate it!

Thu Jan 7 20:48:29 2010: 7887 MitulThakkar

Great Article!! I was struggling to get the relevant info on web, but for a person like me who has very basic knowledge of security , other articles were too heavy.. This is the best one I have seen so far..

Thank you very much for giving us explanation of gpg

Sun Jan 17 20:57:38 2010: 7921 ratb0y

just wanned to say this is a very good tutorial that saves you from loads of troubles. I found it pretty easy and on target.

Congrats

Wed Jan 27 23:26:21 2010: 7958 anonymous

Thank you for writing such a nice and easy to read tutorial. Keep up.

Wed Feb 24 08:56:01 2010: 8129 Mark

The bit of confusion about what it means to sign a message is the difference between "sign" (which includes message encryption) and "clearsign" (which does NOT encrypt the message; it uses your private key to create a hash which can then be decrypted by your public key; the message text remains in the clear). The confusion happens because a clearsigned email begins with the line "-----BEGIN PGP SIGNED MESSAGE-----". Just my 2 cents.

Wed May 5 19:02:21 2010: 8525 sunny

Hi i am struggling in generating keys in windows server 2008. The username is sunny, so how can i modify this "[marge@apl marge]$ gpg --gen-key". what does ' marge@apl ' means. please help me.

Thanks

Wed May 5 19:22:35 2010: 8526 TonyLawrence

[email protected] or whatever it actually is.

Wed May 5 19:24:44 2010: 8527 TonyLawrence

Oh, I see your confusion.

That stuff is just the command prompt. Nothing you would type.

Tue May 11 14:09:00 2010: 8584 anonymous

hi

i have generated my keys and want to export my public key. i tried this command "gpg --armor --export [email protected] > mypk" nothing comes up but when i try this "gpg --armor --export [email protected]" public key block starts and ends with some code in it. what is the command to export it onto C drive.

can i do a quick test by using my public key to encrypt a file without exporting.

If some one sends me the public key, what will be the file extension? and in order to import it do i have keep in specific directory? i came across a .asc extension file what is this? In what format does the exported keys will be?

please help me.

Tue May 11 14:18:33 2010: 8585 TonyLawrence

The "> mypk" put the key in a file called "mypk", in whatever directory you are working in.

You could make that any name you like if your brain dead operating system requires such. For example, to have that able to be opened by clicking on it, you'd use "mypk.txt"

Just another example of why Windows is dumb. You won't understand why I say that, but that's reality.

Fri May 14 01:16:03 2010: 8589 anonymous

I didn't know GPG. But after reading your article, I know at least 95% how it works. this is very good explanation.

Mon Jul 26 18:34:36 2010: 8858 Sunny

hi

we got my legacy company publi key. My admin imported that and when he run the command " gpg --list-keys " he is able to see it. But when i run the same command i am not able to do it? Are these keys user specific or role specific?

Thanks

Sat Aug 28 08:40:01 2010: 8938 habbay

It can't be explained simpler than this. A great job done!

Tue Aug 31 18:11:54 2010: 8944 anonymous

thanks tony, exactly what I needed, very helpful, egon

Thu Sep 23 21:21:09 2010: 8995 ADubey

Mr. Lawrence, thanks for the excellent documentation. This really helped me set up my encryption.

My issue is that I am trying to automate a process to extract data from an Oracle View, write it to a csv file, encrypt the file and FTP it to our bank. I am calling these procedures from an ASPX Web Application using VB.Net.

I set up the encryption with a specific User account used for Service Accounts.

When I run the Web Application and call gpg.exe to encrypt the data file, it will work fine as long as I am logged in as the service account and am in the debug mode of Visual Studio Web Developer.

When I then try to run the Web app from IE, the encryption fails. I have not been able to trap the exact results to determine any messages.

When I call gpg.exe I am using a Process that allows me to pass the Service account credentials. Equivalent to "Run As". This does not solve the problem.

I have tried calling a batch file to launch the gpg. Same result. I tried creating a scheduled task to run a VBS script using the Service account credentials. Again same result.

The only way I can get it to work, is to be logged in to the IIS Server (Windows 2008 64 bit with IIS 7.) and running the Web Application in debug mode from Visual Studio. Anytime I run it from IE, it fails.

I have set the credentials in IIS for the site to be the Service Account.

My next step is to change the IIS Services account from Local Service to the Domain Service account. (For some reason, I have not been able to get Windows Server to accept the different credentials. The service account is a local admin.) I have tried setting the GNUPGHOME to the Service Accounts GNUGP folder. Still not luck.

Below is a sample of the Batch file I am using to launch gpg.exe. (I have also tried to launch gpg.exe directly from the process. This is just a good example of my syntax.)

GNUPGHOME="c:\Users\ServiceAccount\AppData\Roaming\gnupg\" export GNUPGHOME C: cd "\inetpub\wwwroot\BofA_ftp\FTP\" "c:\GNU\GnuPG\gpg.exe" -u "UserName" -r "KeyName" --always-trust --sign --passphrase-fd 0 %PPHrase% --encrypt "DataFile.csv" > gpg --output test123.fil --decrypt test123.gpg gpg: encrypted with 1024-bit ELG-E key, ID BE658B3D, created 2006-11-07 "TEST-MM (Test Machine) " gpg: Signature made Wed 20 Jun 2012 02:08:00 PM EDT using RSA key ID B734C5E2 gpg: Can't check signature: public key not found

But the public keys are present:

81: gpg --list-public-keys /.gnupg/pubring.gpg ------------------------ pub 1024D/6F037C71 2006-11-07 uid "TEST-MM (Test Machine) " sub 1024g/BE658B3D 2006-11-07

Any thoughts why i get the error?

Sat Jun 23 09:53:37 2012: 11140 TonyLawrence

No, sorry. Keep Googling.

Tue Jul 10 15:27:36 2012: 11189 nb

Sir, Very detailed informative article. Thank you very much ......

Sat Oct 6 05:20:59 2012: 11366 anonymous

i must be a slow-witted person because i STILL don't know how to get started using gpg. how do i unzip a .tar file to get to do the gpg?

Sat Oct 6 11:16:45 2012: 11367 TonyLawrence

You aren't slow witted - nothing here told you how to unpack a tar file.

You might have tried googling "tar" though..

By the way, "zip" implies compression. A tar file CAN be compressed, but tar by itself is just an archiver. Modern tars know how to use external compression tools, though, so the point is usually unimportant.

To unpack (and uncompress if indicated) do

tar xvf whateverthefileis.tar

or

tar xvf whateverthefileis.tgz if it's been zipped.

Sat Oct 20 14:02:59 2012: 11392 Michael

Hi. I followed the instructions here, including importing the public key. Yet when I try to decrypt a file I receive the message "gpg: decryption failed: secret key not available". I'm confused. The recipient of the public key does not have to have both public and private keys, correct? Any suggestions for correcting this problem? Thanks.

Sat Oct 20 14:08:07 2012: 11393 TonyLawrence

Well, you've missed something somewhere. Hard to guess what. Read again, read someone else's instructions, repeat your steps - you went wrong somewhere.

Sun Oct 21 11:26:05 2012: 11394 Michael

Thanks for for your response. I did get your example to work. Thanks. Here is our situation: a bank has generated the private/public gpg keys. They sent the public key to us. We successfully imported that key. Are we correct that we should now be able to decrypt a file that the bank encrypts and send to us? If we will not send encrypted files, we do not have to generate keys. Do we understand this correctly? Thank you!

Sun Oct 21 11:36:05 2012: 11395 TonyLawrence

Yes, and vice versa. As I said above:

For example, if you want to send me something, you'd encrypt it using my public key. No one else can decrypt it; only my private key will work. On the other hand, I might be concerned that it really is you sending me a message. In that case, you'd encrypt your message using your private key (this is called "signing"). If I can decrypt it with your public key (presumably I somehow obtained that key and trust that it really is yours), I know that the message really came from you.

Tue Jan 1 07:50:38 2013: 11642 RajeshRS

I have been trying to understand GPG working for the past 4 hours. There have not been a single website, including the so-called official documentation, which could say in simple terms about how we can implement things using GPG. If these "official" sites want their product/concepts reach people they should put things in a simplest way possible.

And your page on GPG is simply the best I have come across on this topic, as far as a starter is concerned. I really wish this page finds a place in the official documentation. Nothing more to say. Hats Off ..!

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