This page contains various tips and tricks for encryption technologies.

====== SSH ======

===== Generate a public key from existing private key =====

[[http://ubuntuforums.org/showthread.php?t=843896|On Linux, using OpenSSH]]

<code bash>
$ ssh-keygen -y -f private-keyfile
</code>

====== PGP/GnuPG ======

===== Un-revoke a key =====

The revocation of a private/public key pair is designed to be un-reversible.
However, it **is** technically possible to remove the revocation signature
from the key. **NOTE:** This is only useful if the revocation has not
left your control. If the key was uploaded, copied or transfered to anybody
else then removing the revocation signature will not have any meaningful
effect.

==== OpenSSH keys ====

[[http://www.gossamer-threads.com/lists/gnupg/users/40163#40163|To remove the revocation signature]]:

<code bash>
# I recommend these steps be performed in a clean/empty directory

# split key into component parts
$ gpg --export therevokedkey > tempkey.gpg
$ gpgsplit tempkey.gpg

# figure out which packet is the revocation
$ gpg --list-packets 0000*.sig

# 'sigclass' of 0x20 = revocation
$ rm (revocationfile).sig

# Re-assemble
$ cat 0000* > fixedkey.gpg

$ gpg --expert --delete-key therevokedkey
$ gpg --import fixedkey.gpg
</code>

==== SSL/TLS ====

See also

  * [[Software development#TLS/SSL testing/verification|Software development > TLS/SSL testing/verification]]
  * [[Windows servers#TLS/SSL support|Windows servers > TLS/SSL support]]