goShift

A basic inline bit shifter for very weak encryption.

WARNING: This is not secure, and is easy to crack (entropy is very low). It's intended only as a proof of concept and an exercise for me to learn Go.

I had a brief play with threading, which was pretty cool.

How it works

The provided key splits each character of the key into 2 3 bit offsets.
- Offsets 0 and 8 are not allowed.
As we iterate over the bytes of the input stream, we iterate over the offsets, and loop when we run out of offsets.
The offsets represent how many places to shift the bits of each byte,
The bits that fall off the end of the byte rotate back to the start.

Using it

Build

go build

Running it

Syntax

cat fileIn.txt | ./goShift command key > fileOut.txt

command is one of

e - Encrypt.
d - Decrypt.

key is a quoted string. Here are some examples:

"OMG This is such a secure encryption key!1!111"
"WHOOPS! I forgot to turn off the bath taps before leaving the house this morning."
"Nah, it's totally fine. My goldfish will drink it all up."
"Ummm... Dude, that's not how goldfish work."
"Shut up"

Example 1 - To the terminal

This will dump the encrypted data straight into the terminal. This is not useful.

echo "Hello" | ./goShift e "A really nice key."

Example 2 - To a file

Let's send the same data to a file.

echo "Hello" | ./goShift e "A really nice key." > encryted.txt

Example 3 - Decrypt text from a file

Let's decrypt what we encrypted.

cat encryted.txt | ./goShift d "A really nice key."

Example 4 - Decrypt text from a file to a file

Let's decrypt what we encrypted.

cat encryted.txt | ./goShift d "A really nice key." > decrypted.txt

Performance

I originally prototyped the algorithm in PHP so that I had fewer things to debug in Go as I was learning it. This therefore created an interesting question: How does the performance compare between the two languages using almost identical implementations?

Here are the tests encrypting, and decrypting a 480MB video.

Performance in PHP

$ ./test/testSpeedPHP /tmp/test.mkv
in=/tmp/test.mkv intermediate=/tmp/e decrypted=/tmp/d
9.0293164764576 MB/s (9467924.553618 B/s).
real    0m53.174s
user    0m52.728s
sys     0m0.891s
8.6207558922402 MB/s (9039517.7304616 B/s).
real    0m55.695s
user    0m55.125s
sys     0m1.033s
cac98da1464113f3e766a31b2dbcfc4b  /tmp/test.mkv
cac98da1464113f3e766a31b2dbcfc4b  /tmp/d

Performance in Go

$ ./test/testSpeedGo /tmp/test.mkv
in=/tmp/test.mkv intermediate=/tmp/e decrypted=/tmp/d
Command: e
Key: A really SECURE key that no one will guess.
Virtual key length: 86
MB/s: 46.78053827639643

real    0m10.262s
user    0m8.872s
sys     0m2.140s
Command: d
Key: A really SECURE key that no one will guess.
Virtual key length: 86
MB/s: 45.9091558475526

real    0m10.457s
user    0m9.073s
sys     0m2.154s
cac98da1464113f3e766a31b2dbcfc4b  /tmp/test.mkv
cac98da1464113f3e766a31b2dbcfc4b  /tmp/d