Encode::Wordlist::PGP - encode/decode hex values using the PGP Word List

    use Encode::Wordlist::PGP qw(:all); # pgp_wordlist_encode(), pgp_wordlist_decode()

    my $fingerprint = "4155 9711 308F 2A21 B9D5  072D 6219 58AF CB50 B5F9"; # this is the author's GPG fingerprint

    print join(" ", pgp_wordlist_encode($fingerprint));

    my $text_version = qq(cranky equipment preshrunk Babylon chairlift
    midsummer brickyard Camelot sentence specialist ahead clergyman flagpole
    bottomless endorse pharmacy spheroid embezzle scorecard Waterloo);

    print pgp_wordlist_decode($text_version);

    print join(" ", pgp_wordlist_encode($fingerprint));
    # prints something like "cranky equipment preshrunk Babylon chairlift midsummer brickyard Camelot [...]"

   print pgp_wordlist_decode($text_version);
   # prints something like "41559711308F2A21B9D5072D621958AFCB50B5F9"

package Encode::Wordlist::PGP;

use warnings;
use strict;

use 5.008; # required for "()" support in unpack()

our $VERSION = '1.11';

use base qw(Exporter);
our @EXPORT_OK = qw(pgp_wordlist_encode pgp_wordlist_decode);
our %EXPORT_TAGS = ( "all" => \@EXPORT_OK );

use Carp qw(croak);

my @wordlist;

@{$wordlist[0]} = qw(
	aardvark absurd accrue acme adrift adult afflict ahead aimless Algol
	allow alone ammo ancient apple artist assume Athens atlas Aztec
	baboon backfield backward banjo beaming bedlamp beehive beeswax befriend
	Belfast	berserk billiard bison blackjack blockade blowtorch bluebird
	bombast bookshelf brackish breadline breakup brickyard briefcase Burbank
	button buzzard cement chairlift chatter	checkup chisel choking chopper
	Christmas clamshell classic classroom cleanup clockwork cobra commence
	concert cowbell crackdown cranky crowfoot crucial crumpled crusade cubic
	dashboard deadbolt deckhand dogsled dragnet drainage dreadful drifter
	dropper drumbeat drunken Dupont dwelling eating edict egghead eightball
	endorse endow enlist erase escape exceed eyeglass eyetooth facial fallout
	flagpole flatfoot flytrap fracture framework freedom frighten gazelle
	Geiger glitter glucose goggles goldfish gremlin guidance hamlet highchair
	hockey indoors indulge inverse involve island jawbone keyboard kickoff
	kiwi klaxon locale lockup merit minnow miser Mohawk mural music necklace
	Neptune newborn nightbird Oakland obtuse offload optic orca payday peachy
	pheasant physique playhouse Pluto preclude prefer preshrunk printer
	prowler pupil puppy python quadrant quiver quota ragtime ratchet rebirth
	reform regain reindeer rematch repay retouch revenge reward rhythm
	ribcage ringbolt robust rocker ruffled sailboat sawdust scallion scenic
	scorecard Scotland seabird select sentence shadow shamrock showgirl
	skullcap skydive slingshot slowdown snapline snapshot snowcap snowslide
	solo southward soybean spaniel spearhead spellbind spheroid spigot
	spindle spyglass stagehand stagnate stairway standard stapler steamship
	sterling stockman stopwatch stormy sugar surmount suspense sweatband
	swelter tactics talon tapeworm tempest tiger tissue tonic topmost
	tracker transit trauma treadmill Trojan trouble tumor tunnel tycoon uncut
	unearth unwind uproot upset upshot vapor village virus Vulcan waffle
	wallet watchword wayside willow woodlark Zulu
);

@{$wordlist[1]} = qw(
	adroitness adviser aftermath aggregate alkali almighty amulet amusement
	antenna applicant Apollo armistice article asteroid Atlantic atmosphere
	autopsy Babylon backwater barbecue belowground bifocals bodyguard
	bookseller borderline bottomless Bradbury bravado Brazilian breakaway
	Burlington businessman butterfat Camelot candidate cannonball Capricorn
	caravan caretaker celebrate cellulose certify chambermaid Cherokee
	Chicago clergyman coherence combustion commando company component
	concurrent confidence conformist congregate consensus consulting
	corporate corrosion councilman crossover crucifix cumbersome customer
	Dakota decadence December decimal designing detector detergent determine
	dictator dinosaur direction disable disbelief disruptive distortion
	document embezzle enchanting enrollment enterprise equation equipment
	escapade Eskimo everyday examine existence exodus fascinate filament
	finicky forever fortitude frequency gadgetry Galveston getaway glossary
	gossamer graduate gravity guitarist hamburger Hamilton handiwork
	hazardous headwaters hemisphere hesitate hideaway holiness hurricane
	hydraulic impartial impetus inception indigo inertia infancy inferno
	informant insincere insurgent integrate intention inventive Istanbul
	Jamaica Jupiter leprosy letterhead liberty maritime matchmaker maverick
	Medusa megaton microscope microwave midsummer millionaire miracle
	misnomer molasses molecule Montana monument mosquito narrative nebula
	newsletter Norwegian October Ohio onlooker opulent Orlando outfielder
	Pacific pandemic Pandora paperweight paragon paragraph paramount
	passenger pedigree Pegasus penetrate perceptive performance pharmacy
	phonetic photograph pioneer pocketful politeness positive potato
	processor provincial proximate puberty publisher pyramid quantity
	racketeer rebellion recipe recover repellent replica reproduce resistor
	responsive retraction retrieval retrospect revenue revival revolver
	sandalwood sardonic Saturday savagery scavenger sensation sociable
	souvenir specialist speculate stethoscope stupendous supportive
	surrender suspicious sympathy tambourine telephone therapist tobacco
	tolerance tomorrow torpedo tradition travesty trombonist truncated
	typewriter ultimate undaunted underfoot unicorn unify universe unravel
	upcoming vacancy vagabond vertigo Virginia visitor vocalist voyager
	warranty Waterloo whimsical Wichita Wilmington Wyoming yesteryear Yucatan
);

# create word => value mappings
my $index;

for ( 0 .. $#{$wordlist[0]} ) {
		$index->{lc @{$wordlist[0]}[$_] } = {
			value     => $_,
			syllables => 2,
		};
}

for ( 0 .. $#{$wordlist[1]} ) {
		$index->{lc @{$wordlist[1]}[$_] } = {
			value     => $_,
			syllables => 3,
		};
}

sub pgp_wordlist_encode {
	my $string = uc(shift);
	
	$string =~ tr/ -//d; # strip separators
	
	croak "illegal characters in string to encode" if $string !~ /^[A-F0-9]+$/;
	croak "string doesn't contain an even number of characters" if length($string) % 2;
	
	my @digits = unpack("(a2)*", $string); # split into two-character hex bytes

	my @words;
	
	foreach my $position (0 .. $#digits) {
	    push @words, $wordlist[$position % 2][hex($digits[$position])];
	}

	return @words;
}

sub pgp_wordlist_decode {
	my $string = shift;

	$string =~ tr/-\n\r/   /;
	$string =~ s/\s+/ /g;
	
	if ($string !~ m/^[\sa-zA-Z]+$/) {
			croak "illegal characters in string to decode";
	}
	
	my @digits;
	
	my $count = 0;
	
	foreach my $word (split / /, $string) {
			my $key = lc($word);
			croak qq("$word" is not in the PGP wordlist) unless $index->{$key};

			# see ALGORITHM in docs below
			if ($count % 2) {
					croak qq("$word" has two syllables when three were expected) if $index->{$key}{syllables} == 2;
			} else {
					croak qq("$word" has three syllables when two were expected) if $index->{$key}{syllables} == 3;
			}

			push @digits, sprintf("%02X", $index->{$key}{value});
			
			$count++;
	}
	
	@digits;
	
}

1;

__END__