`lastresort`(1) – Encode and decode data in base 256 easily typed words

You might expect data encoded in base 256 to be more space efficient than data encoded in base 16 or base 64, but with this particular set of symbols, that is not the case! As a natural consequence of this, you have to type more, not less, when you manually input data using this base 256 encoding instead of base 16 or some other compact representation.

So, why this base 256 encoding?

Manually typing out base 64 is painful. Same goes for base 16. Both of these (base 64 and base 16), and particularly base 16, are prone to make you lose track of where you are while reading and typing or speaking.

lastresort aims to make manual input of binary data onto a computer by either keyboard or voice input less error-prone compared to typing in the base 16 or base 64 encoding of said data.

Here is a quick example:

Imagine a file with three bytes in it. A hexadecimal dump of this file might look like:

text 00000000: 0505 05 ...

In other words, this file contains three bytes 0x05 0x05 0x05.

In base64 this is:

text BQUF

That's not so bad, and it's quick and easy to type or to read out loud in either base 16 or base 64 encoding.

But when the amount of data increases, it becomes more and more tricky to manually type in the bytes by hand or to read them out loud in base 16 or in base 64.

When might you want to type in the bytes of a file by hand, or to read them out loud anyways?

Sample use-cases include:

typing in your SSH private key on a computer that is running a live USB stick copy of its OS without persistent storage, and which doesn't have a usable webcam leaving you unable to enter the data using a QR-code.
relaying the contents of binary files to another person over a voice channel.

Anyways, to continue with the example from above of the three bytes.

In lastresort base 256 using the default codec PGP Word List, the bytes from the example above are represented as:

text adult amulet adult

By now, you should see both:

Why the name of this command is lastresort, and
How in the case of greater amount of bytes, lastresort can be of great help :)

Codecs

lastresort supports the following codecs:

PGP Word List, the default codec
EFF Short Wordlist 2.0, the legacy codec

PGP Word List

The PGP Word List ("Pretty Good Privacy word list", also called a biometric word list [...]) is a list of words for conveying data bytes in a clear unambiguous way via a voice channel. They are analogous in purpose to the NATO phonetic alphabet used by pilots, except a longer list of words is used, each word corresponding to one of the 256 distinct numeric byte values.

[...]

The list is actually composed of two lists, each containing 256 phonetically distinct words, in which each word represents a different byte value between 0 and 255. Two lists are used because reading aloud long random sequences of human words usually risks three kinds of errors: 1) transposition of two consecutive words, 2) duplicate words, or 3) omitted words.

To detect all three kinds of errors, the two lists are used alternately for the even-offset bytes and the odd-offset bytes in the byte sequence. Each byte value is actually represented by two different words, depending on whether that byte appears at an even or an odd offset from the beginning of the byte sequence. The two lists are readily distinguished by the number of syllables; the even list has words of two syllables, the odd list has three. The two lists have a maximum word length of 9 and 11 letters, respectively.

https://en.wikipedia.org/wiki/PGPwordlist

EFF Short Wordlist 2.0

The EFF Short Wordlist 2.0 is a list of 1,296 memorable and distinct words with a few additional features making the words easy to type:

Each word has a unique three-character prefix. This means that future software could auto-complete words in the passphrase after the user has typed the first three characters

All words are at least an edit distance of 3 apart. This means that future software could correct any single typo [...] (and in many cases more than one typo).

https://www.eff.org/deeplinks/2016/07/new-wordlists-random-passphrases

This wordlist is also used in the pgen passphrase generator. See https://github.com/ctsrc/pgen for more about pgen.

In lastresort, 256 of the words from this list are used when using this codec.

Example input and outputs using the different codecs

In the sample_data/original directory of this repository, we have a file named id_ed25519 containing the following OpenSSH ed25519 private key:

text -----BEGIN OPENSSH PRIVATE KEY----- b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW QyNTUxOQAAACCdE5ZT2FyAqO/5dfMJHZ2LsKdK95x1Jo/kJB8es4O2HQAAAJiy+V66svle ugAAAAtzc2gtZWQyNTUxOQAAACCdE5ZT2FyAqO/5dfMJHZ2LsKdK95x1Jo/kJB8es4O2HQ AAAEAAr0Ou+od9Jnc+qb0VTq4zt3gF60+0ITRlL3HybqGLG50TllPYXICo7/l18wkdnYuw p0r3nHUmj+QkHx6zg7YdAAAAEGVyaWtuQGxpYmVyYXRpb24BAgMEBQ== -----END OPENSSH PRIVATE KEY-----

The corresponding base 256 encoded outputs using each of the different codecs available in lastresort are shown is the subsections below.

Example output using the PGP Word List encoder

If we run lastresort with the above private key id_ed25519 as input, and we use the PGP Word List codec:

zsh cargo run -- -e pgp -i sample_data/original/id_ed25519 | fold -w 78 -s

We get the following base 256 encoded output:

text button commando button commando button detergent crusade disable dogsled enchanting bison enrollment drumbeat dinosaur drifter escapade dwelling disbelief bison enterprise Dupont disruptive egghead detector eating dinosaur bison divisive crusade fascinate button commando button commando button armistice flagpole congregate crowfoot hemisphere flagpole hideaway drifter insincere fallout determine chatter impartial enlist exodus Geiger inception flytrap hazardous crusade detector cranky detector cranky detector crowfoot disable chopper inertia flagpole hesitate edict detector cranky detector cranky dinosaur flagpole hesitate classroom indigo enlist equation cranky detector cranky detector cranky detector cranky detector cranky detergent cranky detector cranky detector dreadful infancy cranky detector cranky detector highchair insincere flatfoot conformist framework inception enlist existence allow equation inverse enchanting eating everyday indulge enrollment drunken detector cranky detector crucial determine flytrap dinosaur chopper filament eating conformist cubic informant cranky hydraulic dropper component chopper graduate fragile embezzle dosage disbelief enlist conformist drainage impetus dragnet graduate dragnet crossover chopper inferno chatter distortion goggles component Geiger distortion crowfoot councilman fracture impetus choking enrollment checkup disbelief drunken detector cranky detector dosage handiwork inverse coherence egghead corporate Christmas impetus hotdog hemisphere fracture armistice hockey hamburger cranky detector cranky detector highchair insincere flatfoot conformist framework inception enlist existence drunken informant drifter Eskimo edict inferno dropper equation cranky detector cranky determine crucial graduate crusade consulting enlist Eskimo checkup direction inverse detector gremlin enrollment cement consulting flytrap guitarist dreadful distortion deckhand filament checkup document hamlet divisive flytrap divisive classroom consulting indulge confidence dosage holiness cement headwaters dosage detergent classic gravity hamlet consensus dropper conformist deckhand equation allow detector cranky detector crusade detector cranky impartial chairlift enrollment hockey coherence goggles graduate classroom distortion glucose gossamer briefcase hydraulic flagpole concurrent egghead Eskimo gremlin consensus involve inception chisel hamburger cubic corporate chairlift coherence chairlift disruptive eating equipment Glasgow document chisel disbelief inverse glossary gremlin disable drainage disable chopper concurrent eating hemisphere Glasgow enterprise endow exodus dogsled determine goggles corrosion cement hemisphere chatter councilman indoors headwaters flytrap hideaway endow indigo indoors armistice goldfish concurrent guidance congregate glucose disbelief edict hesitate gazelle coherence drunken headwaters deckhand inferno Christmas insincere framework corrosion endow graduate cranky detector cranky detector crusade disable egghead informant fallout existence highchair indigo drunken disable indulge hurricane endow hesitate egghead informant endow exodus Dupont hurricane flagpole conformist choking detergent cranky hamburger dreadful dinosaur crowfoot equation commence decadence allow commando button commando button commando crusade enchanting crumpled cannonball dropper enterprise crusade enchanting dwelling escapade deckhand cannonball drumbeat equipment dogsled examine cranky Eskimo crusade cannonball dragnet dinosaur endow commando button commando button commando allow

Example output using the EFF Short Wordlist 2.0 encoder

If we run lastresort with the above private key id_ed25519 as input, and we use the EFF Short Wordlist 2.0 codec:

zsh cargo run -- -e eff -i sample_data/original/id_ed25519 | fold -w 78 -s

We get the following base 256 encoded output:

text carrot carrot carrot carrot carrot dealer depot dictionary directory dryer badass dugout dustpan depot dryer ebook ebook dimple badass dustpan eagerness directory eggnog daughter ecosystem depot badass dominoes depot elsewhere carrot carrot carrot carrot carrot alchemy eskimo clay dealer federal eskimo fettuccine dryer geyser ergonomic deepness chopsticks foamless embroidery eliminator faucet fox etiquette falcon depot daughter daughter daughter daughter daughter dealer dictionary codeword gainfully eskimo femur educator daughter daughter daughter daughter depot eskimo femur crawfish frosting embroidery dwelling daughter daughter daughter daughter daughter daughter daughter daughter daughter dealer daughter daughter daughter daughter dresser garlic daughter daughter daughter daughter fox geyser estrogen cinnamon exfoliate fox embroidery elbow alchemy dwelling geographer dryer ecosystem educator gearbox dugout dwelling daughter daughter daughter deepness deepness etiquette depot codeword embroidery ecosystem cinnamon device geographer daughter fleshiness dugout cement codeword etiquette evolution dresser dizziness dimple embroidery cinnamon double fondue dominoes etiquette dominoes crawfish codeword gearbox chopsticks dizziness fictitious cement faucet dizziness dealer couch euthanize fondue clubhouse dugout cinnamon dimple dwelling daughter daughter daughter dizziness fabric geographer cage eggnog cohabitate cohabitate fondue gainfully federal euthanize alchemy frosting exfoliate daughter daughter daughter daughter fox geyser estrogen cinnamon exfoliate fox embroidery elbow dwelling geographer dryer ecosystem educator gearbox dugout dwelling daughter daughter daughter deepness deepness etiquette depot codeword embroidery ecosystem cinnamon device geographer daughter fleshiness dugout cement codeword etiquette evolution dresser dizziness dimple embroidery cinnamon double fondue dominoes etiquette dominoes crawfish codeword gearbox chopsticks dizziness fictitious cement faucet dizziness dealer couch euthanize fondue clubhouse dugout cinnamon dimple dwelling alchemy daughter daughter daughter depot daughter daughter foamless chalkboard dugout frosting cage fictitious etiquette crawfish dizziness fettuccine estrogen cage fleshiness eskimo chalkboard eggnog ecosystem fleshiness clubhouse geyser fox clay exfoliate device cohabitate chalkboard cage chalkboard directory ecosystem eagerness federal double clay dimple geographer eskimo fleshiness dictionary double dictionary codeword chalkboard ecosystem federal federal dustpan elsewhere eliminator directory deepness fictitious copier cement federal chopsticks couch garlic faucet etiquette fettuccine elsewhere frosting garlic alchemy finalist chalkboard foamless clay fettuccine dimple educator femur falcon cage dwelling faucet dimple gearbox cohabitate geyser exfoliate copier elsewhere etiquette daughter daughter daughter daughter depot dictionary eggnog geographer ergonomic elbow fox frosting dwelling dictionary gearbox finalist elsewhere femur eggnog geographer elsewhere eliminator eagerness finalist eskimo cinnamon clubhouse dealer daughter exfoliate dresser depot dealer dwelling cybernetic cybernetic alchemy carrot carrot carrot carrot carrot depot dryer deliverer badass dugout dustpan depot dryer ebook ebook dimple badass dustpan eagerness directory eggnog daughter ecosystem depot badass dominoes depot elsewhere carrot carrot carrot carrot carrot alchemy

Usage

lastresort [-d | --decode] [-i <INPUT_FILE>] [-o <OUTPUT_FILE>] lastresort -h | --help lastresort -V | --version

With no options, lastresort reads raw data from stdin and writes encoded data as a continuous block of space-separated human words to stdout.

Options

-d, --decode [<DECODER>] Decode data (default action is to encode data). Default: pgp. Possible values: pgp, eff.

-e, --encoder <ENCODER> Encoder to use. Possible values: pgp, eff. If encoder is not specified, the pgp encoder will be used. Conflicts with option -d.

-i, --input <INPUT_FILE> Read input from INPUT_FILE. Default is stdin; passing - also represents stdin.

-o, --output <OUTPUT_FILE> Write output to OUTPUT_FILE. Default is stdout; passing - also represents stdout.

-h, --help Print usage summary and exit.

-V, --version Print version information and exit.

Installation

Install Rust.
Run cargo install base256

lastresort(1) – Encode and decode data in base 256 easily typed words