Codecrypt: The post-quantum cryptography tool.
coderman at protonmail.com
Wed Feb 10 01:52:26 PST 2021
The post-quantum cryptography tool.
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.
Go read http://pqcrypto.org/
- infopage: http://e-x-a.org/codecrypt/
- package downloads: http://e-x-a.org/codecrypt/files/
- 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
- Python bindings: https://github.com/mike805/codecrypt-python/
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.
- 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.
- FMTSeq with many possibilities and combinations of aforementioned CRHFs
- SPHINCS256 support is scheduled for next release
- 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.
Cryptography is not intended for "online" use, because some algorithms (especially the MDPC decoding) are (slightly) vulnerable to timing attacks.
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 -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
#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
For completeness I add listing of all options here (also available from ccr --help)
Usage: ./ccr [options]
-h, --help display this help
-V, --version display version information
-T, --test perform (probably nonexistent) testing/debugging stuff
-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
-s, --sign sign a message
-v, --verify verify a signed message
-e, --encrypt encrypt a message
-d, --decrypt decrypt an encrypted message
-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
-g, --gen-key generate keys for specified algorithm
-g help list available cryptographic algorithms
-k, --list list the contents of keyring
-i, --import import keys
-p, --export export keys
-x, --delete delete matching keys
-m, --rename rename matching keys
-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
Codecrypt eats data. Use it with caution. Read the F manual.
Author is a self-taught cryptographer.
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