defuse

<?php

// THIS CODE IS EXPERIMENTAL. DO NOT USE IT.
// ALSO NOTE THERE IS NO ERROR CHECKING!

function side_channel_safe_encode($binary_string)
{
    // We only use 5 bits from every byte, so for 256 bits we need 52 bytes.
    $random = mcrypt_create_iv(52, MCRYPT_DEV_URANDOM);
    $printable_blind_key = '';

defuse

<?php

// WARNING: THIS IS EXPERIMENTAL CODE. DO NOT USE IT.

// --- binary to hex encoding ---

function sc_bin2hex($binary)
{
    $encoded = '';
    for ($i = 0; $i < strlen($binary); $i++) {

defuse

Sketch of a security proof for BCRYPT(H(X)). This probably contains errors.

UPDATE: Only assume BCRYPT is collision resistant for X <= 72.

Define the BCRYPT-H(S, X) algorithm as follows:

UPDATE: Gah... the whole 'byte' thing isn't necessary at all. I originally
intended to pass *either* the actual X (with a zero byte prefix) or H(X) with
a 0x01 byte prefix, to bcrypt. I forgot to do that, and instead always passed
the hash with the byte prefix based on the length. The proof is still valid,

defuse

Keybase proof

I hereby claim:

• I am defuse on github.
• I am defuse (https://keybase.io/defuse) on keybase.
• I have a public key whose fingerprint is BFAE 45EB D356 1D91 E3E2 56C2 DFA8 209C E967 8D5D

To claim this, I am signing this object:

defuse

# This script answers the following question:
# Alice chooses N random numbers between 1 and K.
# Bob chooses G random numbers between 1 and K.
# What is the probability that at least one number is chosen by both of them?

# Computes (K-N choose G) / (K choose G) in O(N)-ish time.

k = 1_000_000_000
n = 10_000
g = 100_000

defuse

# WARNING! There is no warranty. This script might not work!

FILE = "Download.csv"
rows = []

File.open( FILE ) do |f|
  rows = f.readlines()
end

rows = rows[1..-1]

defuse

Goal: 
    You're given a sequence of random alphanumeric characters (0-9a-zA-Z, 62
    possible characters), for example from a password generator. Convert it into
    a sequence of random *bits*.

    The output should have the property:

        The alphanumeric character RNG can be distinguished from random if and
        only if the alphanumeric character RNG, with the conversion algorithm
        attached, can be distinguished from random.

defuse

WARNING: This takes about 10-20 hours to run, depending on your system.
1%...
2%...
3%...
4%...
5%...
6%...
7%...
8%...
9%...

defuse

# This is well-known behavior, it's just interesting.
$ mkdir a
$ echo "hello!" > a/file.txt
$ cat a/file.txt
hello!
$ chmod 000 a/file.txt 
# Now I don't expect to be able to change a/file.txt...
$ echo "GOODBYE" > a/file.txt
bash: a/file.txt: Permission denied
# Okay, good, I can't modify the file directly.

defuse

// WARNING! This code is untested and experimental. DO NOT USE IT.

// NOTE: If I knew of a way to do the "shift and OR" thing reliably with unsigned ints, the code could be simplified a lot.

// Will always be compiled with -std=c99

// Returns UINT32_MAX if a == b, 0 otherwise.
uint32_t invariant_time_integer_compare(uint32_t a, uint32_t b)
{
    /* z will be zero if and only if a == b. */