About NCSA Projects User Info News
 |
Download SELS brochure 
|
List Subscriber
After meeting the prerequisites defined for List Subscriber under Installation, you are ready to subscribe to a secure email list hosted at the NCSA List server . The following picture shows the steps involved.
Let us say you want to subscribe to the secure email list mylist and your email address is testusr@pkirack1.ncsa.uiuc.edu. To do so, please follow these steps. 1. Subscribing to a secure email ListGo to the list page and subscribe to a list using your email address, testusr@pkirack1.ncsa.uiuc.edu. On receiving an email from the List Server, you must confirm your subscription either by replying to the email or following a web link provided in the email. On successful subscription you will receive an acknowledgement email from the List Moderator. 2. Receiving Keys for the ListYou will receive four emails from the List Moderator, which you need to process as described in Installing Keys for the List. Note that the List Moderator executes some manual steps before sending you these emails, therefore, please allow for some time during business hours for these emails to be sent. Email 1The first email with subject "Instructions for setting up keys for mylist testusr(mylist)<testusr@pkirack1.ncsa.uiuc.edu> subscribed to list mylist " contains instructions to follow for the next the two emails the subscriber is going to receive. Email 2The second email with subject "LM public key mylist testusr(mylist)<testusr@pkirack1.ncsa.uiuc.edu>" contains the signature verification key (public-key) of the List Moderator. Email 3The third email is an encrypted and signed message with subject "Accept mylist testusr (mylist) <user@pkirack1.ncsa.uiuc.edu>" from the List Moderator. This email contains three keys, which you require for using SELS. These keys are your individual decryption and encryption keys (for the list) and the list encryption key. Installing Keys for the ListEmail 2You must import the List Moderator's signature verification key, contained in the first email message, into your GnuPG keyring in order to verify the signature on the second message. To do so, save the first email message to a file, say foo.gpg. Then execute the command gpg --import foo.gpg . A sample execution is shown below: $ gpg --import foo.gpg gpg: key DA73F75J: public key "Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>" imported gpg: Total number processed: 1 gpg: imported: 1 You might be able to import the key using the email client user interface and not have to use command line depending on the email client and PGP plugin you are using. Some email clients and plugins (e.g., Thunderbird with Enigmail) allow for importing of keys directly from the email client interface while others don't. Note the key-id of the key imported which is DA73F75J in the example shown above. You need to place 'ultimate trust' in the imported List Moderator's key in your GnuPG keyring prior to its use.To do so you need to execute the command gpg --edit-key keyID where keyID is the 8 character hexadecimal key identifier of the key you just imported (which you noted above). This keyID can also be determined by executing the command gpg --list-keys and looking for the key with name containing the the List Moderator's email-id. NOTE: Prior to placing 'ultimate trust' in this key it is recommended that you authenticate it, for example, by crosschecking the fingerprint ( using command gpg --fingerprint keyid or as shown below) of the key with the list moderator by some out-of-band like telephone . A sample execution is shown below: $ gpg --list-keys
/home/testusr/.gnupg/pubring.gpg
---------------------------------
pub 1024D/DA73F75J 2006-10-31
uid Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
sub 1024g/FF67EAC8 2006-10-31
.
.
.
$gpg --edit-key DA73F75J
pub 1024D/DA73F75J created: 2006-10-31 expires: never usage: SC
trust: unknown validity: unknown
sub 1024g/FF67EAC8 created: 2006-10-31 expires: never usage: E
[ unknown] (1). Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
Command> fpr
pub 1024D/DA73F75J 2006-10-31 Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
Primary key fingerprint: 2B47 2121 93C3 5495 95D8 585C 72DC 9142 DA73 F75J
Command> trust
pub 1024D/DA73F75J created: 2006-10-31 expires: never usage: SC
trust: unknown validity: unknown
sub 1024g/FF67EAC8 created: 2006-10-31 expires: never usage: E
[ unknown] (1). Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
m = back to the main menu
Your decision? 5
Do you really want to set this key to ultimate trust? (y/N) y
pub 1024D/DA73F75J created: 2006-10-31 expires: never usage: SC
trust: ultimate validity: unknown
sub 1024g/FF67EAC8 created: 2006-10-31 expires: never usage: E
[ unknown] (1). Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
Please note that the shown key validity is not necessarily correct
unless you restart the program.
Command> q
$
Email 3You must now decrypt the second email message, verify the signature on it and them import the three keys contained in the message to your GnuPG keyring. To decrypt the email message you require a passphrase. This passphrase will be given to you out-of-band by the List Moderator; e.g., in person or via a telephone call. Once you receive the passphrase save the email message to a file say enc_msg.gpg,. Now, execute the following GnuPG command to decrypt the message and use the passphrase provided by the List Moderator, when prompted. gpg --decrypt enc_msg.gpg > keys.gpg To verify the LM's signature on this email, and decode the keys sent by the LM execute the following GnuPG command. NOTE: To verify the signature on this message you need the LM's signature verification key (public-key) that you received in the first message.This command will fail if you haven't imported the key from the first message. gpg --decrypt keys.gpg > keys Make sure the signature verification succeeded before importing the keys using the following command: gpg --import --allow-secret-key-import keys These steps along with a graphical illustration are provided here. A sample execution is shown below. $gpg --decrypt enc_msg.gpg > keys.gpg gpg: CAST5 encrypted data Enter passphrase: gpg: encrypted with 1 passphrase gpg: WARNING: message was not integrity protected $gpg --decrypt keys.gpg > keys gpg: Signature made 11/1/06 15:13:32 using DSA key ID DA73F75J gpg: Good signature from "Test Moderator <test_mod@pkirack1.ncsa.uiuc.edu>" $gpg --import --allow-secret-key-import keys gpg: key AC0ED7B5: public key "testusr (mylist) <testusr@pkirack1.ncsa.uiuc.edu>" imported gpg: key AC0ED7B5: secret key imported gpg: key AC0ED7B5: "testusr (mylist) <testusr@pkirack1.ncsa.uiuc.edu>" not changed gpg: key 00F3CC43: public key "LK (mylist) <mylist@pkirack1.ncsa.uiuc.edu>" imported gpg: Total number processed: 3 gpg: imported: 2 gpg: unchanged: 1 gpg: secret keys read: 1 gpg: secret keys imported: 1 gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model gpg: depth: 0 valid: 1 signed: 2 trust: 0-, 0q, 0n, 0m, 0f, 1u gpg: depth: 1 valid: 2 signed: 3 trust: 2-, 0q, 0n, 0m, 0f, 0u $ We STRONGLY RECOMMEND changing the password for your list decryption key, to be the same as your own GPG signature key for ease of use. Otherwise you will have to enter different passwords for sending and receiving messages. Either use your GPG plugin's key management interface or the GPG command gpg --edit-key key-id where key-id is the one you have noted in the above step. Type passwd at the command prompt and follow instructions. The initial password is the password you used to decrypt the email message above. Type quit at the command prompt to exit. A sample exeuction is shown below: $gpg --edit-key DA73F75J
pub 1024D/DA73F75J created: 2006-10-31 expires: never usage: SC
trust: unknown validity: unknown
sub 1024g/FF67EAC8 created: 2006-10-31 expires: never usage: E
[ unknown] (1). Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>
Command> passwd
Key is protected.
You need a passphrase to unlock the secret key for
user: "Test Moderator <test-mod@pkirack1.ncsa.uiuc.edu>"
1024-bit DSA key, ID DA73F75J, created 2006-10-31
Enter passphrase:
Enter the new passphrase for this secret key.
Enter passphrase:
Repeat passphrase:
Command> q
Save changes? (y/N) y
$
Email 4The fourth email with subject "Update for user testuser (mylist)<testuser@pkirack1.ncsa.uiuc.edu> of list mylist" is a notification for the user, that his corresponding (or proxy) keys have been generated at the List Server. If a user does not get this information, he should contact the List Moderator. Sending and Receiving Secure EmailsYou are now ready to send and receive secure emails. The email address for the list will be mylist@pkirack1.ncsa.uiuc.edu. When sending an email to the list, you must choose the encrypt option from the email client menu (or encrypt command depending on the email client). The encryption key will be chosen automatically from the keyring. You can additionally choose to sign the email message, for integrity purposes. On receiving a secure email you must decrypt the email to see its contents. To do so your email client will ask for a passphrase that unlocks your decryption key. You can also configure the email client to automatically decrypt incoming email for some clients. Note that for now you can only send and receive secure text messages via SELS. The ability to send secure encrypted attachments will be explored in future version. You may subscribe to more than one secure email list.
Last modified: 01/04/08
|
