GitHub - exaexa/codecrypt: Post-quantum cryptography tool
source link: https://github.com/exaexa/codecrypt
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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/
Links
Distro packages
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/numsdirectory 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.
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