'Decryption' is a valid noun form of the English verb 'decrypt.' It is present in the British dictionary, but it seems to be missing from the US dictionary, see below:
[mbooth@sd ~]$ echo decryption | hunspell -d en_GB
[mbooth@sd ~]$ echo decryption | hunspell -d en_US
& decryption 4 0: encryption, deception, description, decoration
Indeed, seems inconsistent. Filed an upstream bug for this as...
the "decrypt" words are there in the source package, but are considered more "exotic" level 70 words than the "encrypt" family which appear <= level 60 which is the default spell-checking level. I can easily bump this to level 70 to get them in, which I've done for the next release, but ideally decrypt/encrypt would both be of equal level.
hunspell-en-0.20100322-1.fc13 has been submitted as an update for Fedora 13.
hunspell-en-0.20100322-1.fc12 has been submitted as an update for Fedora 12.
hunspell-en-0.20100322-1.fc12 has been pushed to the Fedora 12 stable repository. If problems still persist, please make note of it in this bug report.
hunspell-en-0.20100322-1.fc13 has been pushed to the Fedora 13 stable repository. If problems still persist, please make note of it in this bug report.