alea = 'QUxFQSD4A7SPYPK/qZVDzskNohowqhLukG6ZyBfIx5/1FZf+DpqynvulXaQ7oHIFrhU='.unpack('m').first[5,45]
chal = 'Q0hBTExFTkdFII/JtptN9pii+JcTxjNk/jU='.unpack('m').first[10, 16]
pad  = "\x7A\x61\x65\x28\x27\x5F\x5D\x66\x34\x60\x23\x63\x38\x34\x67"
user = "alice\n"

if false

user = "alice\n"
alea = "012345678901234567890123456789012345678901234"
foochal = "V^J]\\@}\004\035cjgvmX\024"
pass = "testicule"

bla = user + alea + pass
bla.reverse!
bla += pad[0..3]
chal = bla[0..15]
16.times { |i|
	chal[i] ^= bla[16+i] ^ bla[32+i] ^ bla[48+i]
}
end

bla = (user + alea).reverse + pad

(5..13).each { |passlen|
	foo = chal[0..passlen] + bla
	
	16.times { |i|
		foo[i] ^= foo[16+i] ^ foo[32+i] ^ foo[48+i]
	}
	p foo[0..passlen].reverse
}