Getting an SMIME certificate

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Certificate Authorities

Sources of Free SMIME Certificates

Free certificates usable for S/MIME are available from:

Some of them are free only for personal use. IdenTrust (TrustID Personal Certificate) and Thawte also used to offer free certificates.

Free Certificates from Comodo

Comodo has perhaps one of the easiest procedures for requesting a certificate. They are free, good for a year, can be picked up using most browsers, and can be either 1024 or 2048 bits long. Note that, while the certificate is fully valid for mail clients, "Comodo Trust Network - PERSONA NOT VALIDATED" is registered as the Organizational Unit (OU) in Subject. With Comodo it is possible to create a certificate that contains a fantasy name e.g. "Elvis Undead" <elvis.salt.x4yt@gmail.com>. Does it make sence to include this authority in the database of trusted authorities contained in Mozilla applications? Are digital signatures without any validation of the person really useful?

Free Certificates from Verisign

Similar free (demo, really) certificates are offered by VeriSign - just click the buy button but then choose the free option. Their demo certificates are valid for only 60 days while the paid-for one (20USD) lasts a year. VeriSign runs a free LDAP service that is compatible with Netscape, Mozilla, Thunderbird, Outlook, and Outlook Express so your friends can look-up your certificate automatically while composing email to send you encrypted email.

Free Certificates from GlobalSign

GlobalSign offers a free demo certificate at GlobalSign. Their demo certificates are valid for only 30 days while the paid-for one (20USD) lasts a year. See GlobalSign's Range of Digital Certificates for information on what certificates they sell.

To obtain certificate from an authority

Browsers such as Firefox, MSIE, Opera, Safari and so forth contain cryptotools capable of generating public/private keypairs. When signing up for a certificate with an authority, their website triggers your browser to create a keypair and transmit to them the public key, which is then certified. For this reason, when you return to pick up your completed certificate (typically a few minutes later), it is mandatory that you do so with the same browser on the same computer . You will othewise not possess the private key necessary for pickup.

It will then still be necessary to export the resulting new key and certificate to a regular but password protected file that can then be imported into Thunderbird's certificate store. The CA's and/or your browsers help files should explain how to export your new certificate and keys.

To import the exported keys into Thunderbird, "Tools -> Options -> Advanced -> Encryption -> View Certificates -> Import".

Once you have imported your certificate into Thunderbird, it will then be available for pairing with one or more accounts in Thunderbird. Account Settings -> Security -> Select.

Be thoughtful about whether to select to "digitally sign all messages by default". Institutional firewalls may protect their own security protocols and break your cryptographic signature, leaving your recipient with all kinds of warnings about the message being invalidly signed. As S/MIME usage is still not widespread, most people still don't know how to interpret this. A broken signature will probably seem worse to them than receiving a message with no crypto signature at all, even though the contents are identical in both cases.

Webmail users will see an unreadible attachment which can raise simliar questions.

Self-signed certificates

You may use a personally self-signed certificate in Thunderbird. However, since these certificates are not signed by an approved certificate authority, the certificate will not be trusted by other computers or people unless they add the self-signed certificate to their list of certificate authorities. Personally self-signed certificates are generally only useful for testing or for exchanging information with people you already know and trust.

It's possible to generate self-signed certificates using the Firefox Add-on Key Manager: Tools - Key Manager Toolbox - Key Manager - Your Keys - Generate SelfSign Cert and insert you data. On tab Advanced - Standard X.509 Extensions check "Is CA?".

Another option for those who have sufficient understanding of certificate structures is using the command line OpenSSL.

Special considerations for installing personally self-signed certificates can be found in the Installing an SMIME certificate article.

Self-signed certificates in Mac OS X 10.4

You can create your own self-signed certificate using the Keychain Access application's Certificate Assistant. To export your certificate as a PCKS12 file for import into Thunderbird, click "My Certificates" in the Keychain Access window. Select your self-signed certificate. Then from the menu bar select "File -> Export". You will be asked for a password to protect this file. This is the password you will require when importing the certificate into the "Your Certificates" tab of Thunderbird after entering your master password.

To export your certificate as a ".cer" file for use as a certificate authority, select "Certificates" in the Keychain Access window. Select your self-signed certificate. Then from the menu bar select "File -> Export". Be sure ".cer" is selected as the appropriate file type in the save dialog.

Other uses for certificates

Free certificates are not necessarily limited to use only by S/MIME email. The same digital id's can be imported and employed during document generation, for example, by ...

  • Adobe Acrobat for signing and encrypting pdf documents. This requires the non-free Acrobat to generate. The free Adobe Reader is available to decrypt and verify.
  • OpenOffice also contains some signing capability using certificates.

These have the advantage over S/MIME in that they pass more easily through firewalls, but at the price of requiring more steps to generate.

See also

External links