Didatic Feedback Cipher Long 2

[MerickOWA]

This challenge done on big endian or little endian machine?

or to be more specific..

(txt -> txt[i + 3]) ^ k

would txt correspond to the least significant byte of k or the most?

[niteria]

I would be happy if I knew what "->" means.

[tails]

Shhh!

The endianness is the most interesting factor of this challenge. The real key is whether you get aware of it, rather than finding the value of x. So why don't you try both?

[therethinker]

@niteria: hopefully I'm not disclosing too much info by saying this... but I don't think the point of the challenge was to understand the -> symbol, so I should be fine

Its best explained with an example... lets say txt = {0x12, 0xab, 0xcd, 0xef}, then txt[0] -> txt[3] would be 0x12abcdef.

[niteria]

thanks, i was too lazy to guess it

[m!nus]

k = {unknown 4-byte value}
x = {unknown 4-byte value}
for (i = 0; i < len(txt); i += 4)
c = (txt -> txt[i + 3]) ^ k
print c
k = (c + x) % 0x100000000 // => mod to 1 byte length
wouldn't be the c in the second iteration be 3 plain bytes and one XORed? seems strange to me

[tails]

k = {unknown 4-byte value}
x = {unknown 4-byte value}
for (i = 0; i < len(txt); i += 4)
c = (txt -> txt[i + 3]) ^ k
print c
k = (c + x) % 0x100000000 // => mod to 1 byte length
wouldn't be the c in the second iteration be 3 plain bytes and one XORed? seems strange to me

Maybe you are dividing instead of modding.