jpauli / php-crypto Goto Github PK

This is a demo of some crypto algos.

A simple Galois based Linear Feedback Shift Register (LFSR).
LFSR are used in computer industry for many applications, like PRNG
One example application is a stream cipher, which is also provided.

RC4 is also provided, other algos could follow


Provided using the PHP language PHP >= 8.1
Also using C, as PHP extension PHP >= 7.0



LFSR Example :
--------------

lfsr_demo.php seed degree

> ./lfsr_demo.php "my secret" 7

**Simple Galois LFSR, degree 7 (127 states m-sequence)**
Used register bits for feedback : 7 6
Deducted Feedback function      : 1100000 (0X60) 


Your initial state is : 00000000000000000000001110001100 (908)
Let's now start the Linear Feedback Shift Register


[Iteration] [-------Internal Register -------] [PRandom bit]
    |                      |                        |       
    v                      v                        v       
         0 - 00000000000000000000001110001100     [ 0 ]
         1 - 00000000000000000000000111000110     [ 0 ]
         2 - 00000000000000000000000011100011     [ 1 ]
         3 - 00000000000000000000000000010001     [ 1 ]
         4 - 00000000000000000000000001101000     [ 0 ]
         5 - 00000000000000000000000000110100     [ 0 ]
         6 - 00000000000000000000000000011010     [ 0 ]
         7 - 00000000000000000000000000001101     [ 1 ]

         ...


StreamCipher example :
----------------------

stream_cipher_demo.php seed

> echo "bar baz an burz" | ./stream_cipher_demo.php "wow, that is secret"

Your input data is 'bar baz an burz'
We are now going to crypt it byte per byte 


Random byte got from LFSR : 11111100

Next byte from your input : 01100010 (b)

------------------------------------

XORed crypted output byte : 10011110



Random byte got from LFSR : 11111101

Next byte from your input : 01100001 (a)

------------------------------------

XORed crypted output byte : 10011100



Random byte got from LFSR : 11111101

Next byte from your input : 01110010 (r)

------------------------------------

XORed crypted output byte : 10001111

... ...


RC4 example :
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> ./RC4_demo.php "my secret key is foobar"

PRB : 99
PRB : C4
PRB : 2A
PRB : 0F
PRB : 5B
PRB : BB
...