Simple block-code encryption algorithm by Hellerick

# Simple block-code encryption algorithm by Hellerick, 2013-06-01
# http://codepad.org/SulkRkYi

from random import randint

code="""z 5 6 7 8 9
0 a b c d e
1 f g h i j
2 k l m n o
3 p q r s t
4 u v w x y"""

code=code.split('\n')
c2l=[]
for i in code: c2l+=[i.split(' ')]
l2c={}
for i in range(len(c2l)):
    for j in range(len(c2l[i])):
        l2c[c2l[i][j]]=[i,j]

def encrypt(text):
    output=cp=c2l[randint(0,len(c2l)-1)][randint(0,len(c2l[0])-1)]
    text=text.lower()
    for i in range(len(text)):
        if text[i] in l2c:
            di,dj=(l2c[text[i]][0]-l2c[cp][0])%6,(l2c[text[i]][1]-l2c[cp][1])%6
            cp=c2l[di][dj]
            output+=cp
        else:
            output=output+text[i]
    return output

def decrypt(text):
    cp=text[0]
    text=text[1:]
    output=''
    for i in range(len(text)):
        if text[i] in l2c:
            di,dj=(l2c[text[i]][0]+l2c[cp][0])%6,(l2c[text[i]][1]+l2c[cp][1])%6
            cp=text[i]
            output+=c2l[di][dj]
        else:
            output=output+text[i]
    return output

thetext="The worst thing about my sister is she's such a GIRL. Well, I'm a girl too, but I'm not a dinky-pinky, silly-frilly girlie girl. Think cupcakes and cuddly teddies and charm bracelets -- that's Melissa. She leaves a little pink trail around the house -- sparkly slides and ribbons and notebooks. You breathe in her revolting scent long after she's gone off to hang out at her friends' houses. She's not allowed to wear real perfume yet, but she's got this rose hand cream that smells really strongly. She doesn't just rub it on her hands, she smoothes it in all over, so she's always slightly slippery. Her lips shine too, because she's forever smearing on lip gloss. She's not really supposed to wear make-up yet either, only for play, but she's got a big plastic bag patterned with pink kittens, and it's crammed full of eye shadows and mascara and blisher. It used to be just Mum's old stuff, but now Melissa spends half her pocket money in Superdrug."

print ' '+thetext
print '\n'
print encrypt(thetext)
print '\n'
print ' '+decrypt(encrypt(thetext))