NaCL bindings for q/kdb.

##Loading

You can load qsalt with:

.qsalt:@[`qsalt 2:(`qsalt;1);0]

##Public Key Authenticated Encryption

Generate (public;private) keypair:

alice:.qsalt.pkey`
bob:.qsalt.pkey`

Alice creates a ciphertext message for Bob:

message:.qsalt.pencrypt[(.qsalt.nonce`;"this is secret");bob 0;alice 1]

Bob decodes the ciphertext message:

.qsalt.pdecrypt[message;alice 0;bob 1]

If the ciphertext has been corrupted or was not created by Alice, then null will be returned.

##Public Key Signatures

Generate (public;private) keypair:

alice:.qsalt.newkey`
bob:.qsalt.newkey`

Alice signs a message for Bob. Note that the message is not encrypted.

message:.qsalt.sign["this is verified";alice 1]

Bob then verifies the signature:

.qsalt.verify[message;alice 0]

If the signature is invalid, then null will be returned.

##Secret Key Authenticated Encryption

There are several ways to generate a secret key; it can be any 32 random bytes:

secret:.qsalt.random32`

Encrypting a message requires a nonce; this nonce must not be reused:

message:.qsalt.sencrypt[(.qsalt.nonce`;"this is also secret");secret]

Decrypting the message also verifies it:

.qsalt.sdecrypt[message;secret]

If the message was altered, then null will be returned.

##Hashing

Calculates the SHA512 hash of a string/bytearray:

.qsalt.hash "whatever"

##Comparing Strings

.qsalt.cmp16 and .qsalt.cmp32 are constant-time comparison functions and should be used for comparing byte-strings.

.qsalt.cmp16["this is sixteen!";"this is sixteen!"]
.qsalt.cmp16["this is sixteen!";"somethinginvalid"]

Building

The makefile assumes kdb/q is installed in $HOME/q and that you have k.h installed in $HOME/q/c:

q/c/k.h

qsalt requires NaCL. On Debian systems you can install:

sudo apt-get install libsodium-dev

then build with:

make nacl=-lsodium arch=64

Note if you're building for the 32-bit version of KDB you will need:

sudo apt-get install libsodium-dev:i386

then build with:

make nacl=-lsodium arch=32

on other systems you install it from The NaCL homepage; You can unpack it directly into this tree:

wget http://hyperelliptic.org/nacl/nacl-20110221.tar.bz2
bunzip2 < nacl-20110221.tar.bz2 | tar -xf -
(cd nacl-20110221 && ./do)

Then to build:

make nacl=nacl-20110221/build/*/lib/amd64/libnacl.a

As a convenience, tweetnacl is included, and can be used with:

make nacl=tweetnacl.c arch=32
make nacl=tweetnacl.c arch=64

geocar/qsalt