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README: some information about used cryptography

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Mirek Kratochvil 2016-04-17 15:09:39 +02:00
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@ -11,6 +11,61 @@ 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.
##### Used cryptography
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 where 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.
KeyID's are CUBE256 hashes of serialized public key.
- 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.
#### Why this?
Go read http://pqcrypto.org/
@ -22,13 +77,16 @@ 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: currently in mentors processing, use `debian/rules mk-orig-source && gbp buildpackage`.
- 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: currently in mentors processing, use `debian/rules
mk-orig-source && gbp buildpackage`.
- Arch linux: see https://aur.archlinux.org/packages/codecrypt/
#### 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
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
## Quick How-To