Toy Tetragraph Hash

At my  Security Computer course i was asked in one of my exercise to build a machine that imitiate Hash procedure.But instead of bits the hash input is chars.

The mechanism of the hash function is illustrated here:

and that is the small python code to compute the hash function:

import numpy as np

text="I leave twenty million dollars to my friendly cousin Bill"

text="AYHG" +"A"*12 +"A"*32

print(text)

#this is the input for the tth...

IV=(0,0,0,0) # initial Vector

def shiftlist(l,n):  #this function do the shift list

    l=list(l)

    Shifted=l[n:]+l[:n]

    return Shifted

text=text.replace(" ",'') #ignore spaces

text=text.lower()         #ignore case sensitive

text=[ord(c)-97 for c in text] #convert text to ascii

lenght = len(text) # move 16 char every time..

for x in range(int(lenght/16)):

    Matrix =np.array(text[16*x:16*(x+1)]).reshape(4,4) #convert 16 string to 4X4 matrix

    

    sumMatrix=(Matrix.sum(axis=0)) #sum the Matrix

    for x in range(3):   # rotate each row

        Matrix[x,:] =shiftlist(Matrix[x,:],x+1)

    #ugly last row rotation:

    temp =Matrix[3,0];Matrix[3,0]=Matrix[3,3];Matrix[3,3]=temp

    temp =Matrix[3,1];Matrix[3,1]=Matrix[3,2];Matrix[3,2]=temp

    ##Sum the  columns + the rotate colums +IV

    

    IV=(IV +(Matrix.sum(axis=0))+sumMatrix)%26

    

#now IV is the output

for i in range(4):  #print the string

    print(chr(IV[i]+97),end=" ")

#######################################################

The next challange is to find a collision.

i leave it as a riddle for you.