hex-fingerprint-words

#!/bin/bash

# This script converts the hexadecimal represenatation of an SSH (or similar) key's fingerprint into friendly words.  The goal is to allow humans to more easily recognize when a fingerprint changes.
# Usage: provide the hexadecimal fingerprint as standard input.  The regex match should trim any excess, so you do not have to be too precise when doing this.  Just make sure that the fingerprint echoed back matches what you expect.
# This version was made in a pinch and has room for improvement.

# Example:
# $ ssh-keygen -l -f ~/.ssh/id_rsa | ./hex-fingerprint-words
# Generating from input fingerprint: 3b:44:c7:20:21:8c:81:5b:af:6a:da:bd:ab:29:c9:4f
# CONSENSUS   DASHBOARD   SHAMROCK    BOTTOMLESS  BRADBURY    MOLECULE    KLAXON      EXAMINE     RACKETEER   GOLDFISH    SURMOUNT    RINGBOLT    PUPIL       CANNONBALL  SLINGSHOT   DRIFTER

word_bank=(
aardvark
accrue
adrift
adult
afflict
aggregate
aimless
alkali
almighty
ammo
amusement
antenna
apple
armistice
artist
asteroid
Atlantic
atmosphere
Aztec
Babylon
backward
banjo
beaming
beehive
befriend
belowground
bifocals
bison
blockade
bluebird
bombast
bookshelf
bottomless
Bradbury
Brazilian
breakaway
brickyard
Burbank
businessman
button
Camelot
cannonball
caravan
celebrate
cement
chairlift
chatter
Cherokee
chisel
chopper
clamshell
classroom
clergyman
cobra
combustion
commence
component
concurrent
conformist
consensus
corporate
councilman
crackdown
crossover
crucial
crumpled
cubic
customer
dashboard
decadence
decimal
designing
detergent
dictator
direction
disbelief
distortion
dogsled
drainage
drifter
drumbeat
Dupont
eating
egghead
embezzle
endorse
enlist
enterprise
equipment
escapade
Eskimo
examine
existence
eyeglass
facial
fascinate
finicky
flatfoot
forever
fracture
freedom
frighten
Galveston
Geiger
glitter
glucose
goldfish
graduate
gremlin
guitarist
Hamilton
handiwork
headwaters
hesitate
highchair
holiness
hydraulic
impetus
indigo
indulge
infancy
informant
insurgent
intention
inverse
island
Jamaica
Jupiter
kickoff
klaxon
letterhead
locale
maritime
maverick
megaton
microscope
midsummer
minnow
miser
Mohawk
molecule
monument
mural
narrative
necklace
newborn
nightbird
Oakland
October
Ohio
optic
orca
outfielder
pandemic
paperweight
paragraph
passenger
peachy
Pegasus
perceptive
pharmacy
phonetic
physique
playhouse
pocketful
positive
preclude
preshrunk
processor
prowler
puberty
pupil
pyramid
quadrant
quiver
racketeer
ratchet
rebirth
recover
regain
rematch
repellent
reproduce
responsive
retraction
retrospect
revenue
revolver
rhythm
ringbolt
rocker
sailboat
sardonic
savagery
scallion
scenic
Scotland
select
sentence
shamrock
skullcap
slingshot
snapline
snowcap
sociable
southward
soybean
spearhead
speculate
spheroid
spindle
stagehand
stairway
stapler
sterling
stockman
stormy
sugar
surmount
suspense
sweatband
sympathy
talon
tapeworm
tempest
tiger
tobacco
tomorrow
topmost
tracker
transit
travesty
Trojan
trouble
tumor
tycoon
ultimate
undaunted
unearth
unify
unravel
upcoming
upset
vacancy
vapor
village
virus
vocalist
Vulcan
wallet
watchword
wayside
Wichita
Wilmington
Wyoming
Yucatan
)

while IFS= read -r hex_fingerprint; do # Read a line of standard input
	hex_fingerprint="$(grep -Eio '([a-f0-9]{2}:)+[a-f0-9]{2}' <<<"$hex_fingerprint" )" || continue # If the line contains something that looks like hex, then try to parse it
	printf '%s %s\n' 'Generating from input fingerprint:' "$hex_fingerprint" # Print the string that looks like hex for added feedback
	hex_buffer=$hex_fingerprint # Initialize a buffer to work with, contents equal the hex string
	while (( ${#hex_buffer} >= 2 )); do # While there are at least two characters of hex...
		hex_byte=${hex_buffer:0:2} # Take the first two characters
		dec_byte=$(printf '%d' "0x${hex_byte}") # Get the decimal value
		printf '%-12s' ${word_bank[$dec_byte]^^} # Print from the word bank at that position
		(( ${#hex_buffer} == 2 )) && break # If these were the last two characters of the hex string, stop
		hex_buffer=${hex_buffer#$hex_byte":"} # Remove the current byte and its tailing colon from the beginning of the buffer
	done
	printf '\n'
done < /proc/self/fd/0