Jon Callas <jon(_at_)callas(_dot_)org>:
kryptobunny(_at_)freedom(_dot_)net:
Benefits from saving a few bytes in PGP sigs:
PGP users 4 M
(original business plan claim)
bytes saved per sig 3
sigs per user 100
---
total bytes saved 1.2 G
The byte savings you put assumes that you have a disk with a 1 byte block
size. Typically, block sizes on disks are larger. Suppose you have a disk
with an 8K block size. Changing a file from 3000 bytes to 2999 bytes saves
nothing. You only really save space if the file that contains a structure
changes the block count of the file.
But in this case you save 8K bytes at once. If the file size modulo
the block size is roughly uniformly distributed, then you have expected
savings of one actual byte of disk space for each byte of file size.
(Actually it's the fragment size, not the block size, that counts.
Since 4.3 BSD, file sytems don't waste a complete block for the final
bytes of a file. Instead a block can be shared for the final
fragments of multiple files. This is more likely to be 1K than 8K,
so even if you usually have rather short messages you will often
use more than one fragment.)
Also there can be multiple signatures in the same file (mbox for example).
And some folks even back up their disks (often using compression so
that block sizes are not an issue). Tapes are cheaper per GB than
hard disks, but there'll usually be multiple copies of the same files.