Codecrypt

The post-quantum cryptography tool.

Codecrypt is currently unmaintained, although I still successfully use it. If you are interested in developing/maintaining it, ping me.

About

This is a GnuPG-like unix program for encryption and signing that uses only quantum-computer-resistant algorithms:

McEliece cryptosystem (compact QC-MDPC variant) for encryption
Hash-based Merkle tree algorithm (FMTSeq variant) for digital signatures

Codecrypt is free software. The code is licensed under terms of LGPL3 in a good hope that it will make combinations with other tools easier.

Why this?

Go read http://pqcrypto.org/

Distro packages

Gentoo packages: https://packages.gentoo.org/packages/app-crypt/codecrypt with current ebuild usually available at http://e-x-a.org/codecrypt/files
Debian packages: apt-get install codecrypt
Arch linux: see https://aur.archlinux.org/packages/codecrypt/
Windows port is maintained separately here: https://github.com/mike805/codecrypt-win32

Language wrappers:

Python bindings: https://github.com/mike805/codecrypt-python/

Documentation

There is a complete, UNIXy manual page supplied with the package. You can view it online here: http://e-x-a.org/codecrypt/ccr.1.html

Used cryptography overview

To achieve the stated goal, codecrypt uses a lot of (traditional, but "quantum-secure") cryptographic primitives. Choices of primitives were based on easy auditability of design, simplicity and provided security.

The git repo of codecrypt contains doc/papers with an unsorted heap of academic papers and slides about relevant topics.

Stream ciphers used:

ChaCha20, the recommended choice from djb
XSynd stream cipher as an interesting and nontraditional candidate also based on assumptions from coding theory; used NUMS (it requires lot of NUMS) are explained in doc/nums directory in the repo.
Arcfour for initial simplicity of implementation. After recent statistical attacks I cannot recommend using any RC4 variant anymore, but provided padding and the "offline-only" usage of codecrypt keeps the usage mostly secure.

CRHFs used:

Cubehash variants were selected for implementation ease, really clean design, quite good speed and flexibility of parameter choices. This is also the only hash possibility when Crypto++ library is not linked to codecrypt. KeyIDs are CUBE256 hashes of corresponding serialized public keys.
ripemd128 for small hashes
tiger192 is used as an alternative for Cubehash for 192bit hashes
There's always a variant with SHA-256, SHA-384 or SHA-512.

Signature algorithms:

FMTSeq with many possibilities and combinations of aforementioned CRHFs
SPHINCS256 support is scheduled for next release

Encryption algorithms:

MDPC McEliece on quasi-cyclic matrices. The implementation uses some tricks to speedup the (pretty slow) cyclic matrix multiplication (most notably libfftm3 in this version). For padding using the Fujisaki-Okamoto scheme, the cipher requires a stream cipher and a CRHF, used ciphers and CRHFs are specified in the algorithm name -- e.g. MCEQCMDPC128FO-CUBE256-CHACHA20 means that the parameters are tuned to provide 128bit security, uses CUBE256 hash, and ChaCha20 stream cipher.
Quasi-dyadic McEliece was included in codecrypt as an original algorithm, but is now broken and prints a warning message on any usage.

Caveats:

Cryptography is not intended for "online" use, because some algorithms (especially the MDPC decoding) are (slightly) vulnerable to timing attacks.

Quick How-To

Everything is meant to work mostly like GnuPG, but with some good simplicity margin. Let's play with random data!

ccr -g help
ccr -g sig --name "John Doe"    # your signature key
ccr -g enc --name "John Doe"    # your encryption key

ccr -K  #watch the generated keys
ccr -k

ccr -p -a -o my_pubkeys.asc -F Doe  # export your pubkeys for friends

#(now you should exchange the pubkeys with friends)

#see what people sent us, possibly check the fingerprints
ccr -inaf < friends_pubkeys.asc

#import Frank's key and rename it
ccr -ia -R friends_pubkeys.asc --name "Friendly Frank"

#send a nice message to Frank (you can also specify him by @12345 keyid)
ccr -se -r Frank < Document.doc > Message_to_frank.ccr

#receive a reply
ccr -dv -o Decrypted_verified_reply.doc <Reply_from_frank.ccr

#rename other's keys
ccr -m Frank -N "Unfriendly Frank"

#and delete pukeys of everyone who's Unfriendly
ccr -x Unfri

#create hashfile from a large file
ccr -sS hashfile.ccr < big_data.iso

#verify the hashfile
ccr -vS hashfile.ccr < the_same_big_data.iso

#create (ascii-armored) symmetric key and encrypt a large file
ccr -g sha256,chacha20 -aS symkey.asc
ccr -eaS symkey.asc -R big_data.iso -o big_data_encrypted.iso

#decrypt a large file
ccr -daS symkey.asc <big_data_encrypted.iso >big_data.iso

#password-protect all your private keys
ccr -L

#protect a symmetric key using another symmetric key
ccr -L -S symkey1 -w symkey2

#password-protect symkey2 with a custom cipher
ccr -L -S symkey2 -w @xsynd,cube512

Option reference

For completeness I add listing of all options here (also available from ccr --help)

Usage: ./ccr [options]

Common options:
 -h, --help     display this help
 -V, --version  display version information
 -T, --test     perform (probably nonexistent) testing/debugging stuff

Global options:
 -R, --in      set input file, default is stdin
 -o, --out     set output file, default is stdout
 -E, --err     the same for stderr
 -a, --armor   use ascii-armored I/O
 -y, --yes     assume that answer is `yes' everytime

Actions:
 -s, --sign     sign a message
 -v, --verify   verify a signed message
 -e, --encrypt  encrypt a message
 -d, --decrypt  decrypt an encrypted message

Action options:
 -r, --recipient    encrypt for given user
 -u, --user         use specified secret key
 -C, --clearsign    work with cleartext signatures
 -b, --detach-sign  specify file with detached signature
 -S, --symmetric    enable symmetric mode of operation where encryption
		    is done using symmetric cipher and signatures are
		    hashes, and specify a filename of symmetric key or hashes

Key management:
 -g, --gen-key        generate keys for specified algorithm
 -g help              list available cryptographic algorithms
 -k, --list           list the contents of keyring
 -K, --list-secret
 -i, --import         import keys
 -I, --import-secret
 -p, --export         export keys
 -P, --export-secret
 -x, --delete         delete matching keys
 -X, --delete-secret
 -m, --rename         rename matching keys
 -M, --rename-secret
 -L, --lock           lock secrets
 -U, --unlock         unlock secrets

Key management options:
 -F, --filter       only work with keys with matching names
 -f, --fingerprint  format full key IDs nicely for human eyes
 -N, --name         specify a new name for renaming or importing
 -n, --no-action    on import, only show what would be imported
 -w, --with-lock    specify the symmetric key for (un)locking the secrets
 -w @SPEC           ask for password and expand it to a symmetric key
                    of type SPEC for (un)locking the secret

Disclaimer

Codecrypt eats data. Use it with caution. Read the F manual.

Author is a self-taught cryptographer.

exaexa/codecrypt

exaexa

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