changing character base, need adding some xoring somewhere

change_charset.rb

# Optimised if the BASE array has the same size as a power of 2, otherwise disable symetrie
# Optimised if 0 is the first in the BASE array
BASE_2 = ['0','1']
BASE_4 = ('0'..'3').to_a
BASE_8 = ('0'..'7').to_a
BASE_16 = ('0'..'9').to_a + ('a'..'f').to_a
BASE_32 = ('0'..'9').to_a + ('a'..'v').to_a
BASE_64 = ('0'..'9').to_a + ('a'..'z').to_a + ('A'..'Z').to_a + ['$','_']
SHUFFLE_BASE_16 = ['0','4','2','1','8','6','7','5','9','3','c','b','a','f','d','e']
SHUFFLE_BASE_64 = ['0','7','S','q','j','6','N','C','u','8','W','k','4','J','K','5','m','1','F','f','D','X','g','V','n','z','B','i','L','P','l','a','G','s','Q','2','Z','d','v','o','I','x','_','M','Y','c','9','h','$','R','b','U','y','O','A','w','e','p','3','T','E','H','t','r']

def change_charset(str, f, t)
  def bin_fix_length(b, s)
    b = '0' + b while b.length < s
    b
  end

  l = (f.length - 1).to_s(2).length
  str_c = ''
  while str != ''
    str_c += bin_fix_length(f.index(str.slice!(0)).to_s(2), l)
  end
  
  str_c.slice!(0) while str_c.slice(0) == '0'

  l = t.length.to_s(2).length - 1
  s = (str_c.length.to_f / l).ceil * l
  str_c = bin_fix_length(str_c, s)
  while str_c != ''
    str = t[str_c.slice!(-l,l).to_i(2)] + str
  end

  str
end

change_charset(Digest::SHA1.hexdigest("1445"), BASE_16, BASE_64) # 64 = 2^6, 16 = 2^4 => compression = 4/6
a = change_charset('17',SHUFFLE_BASE_16, SHUFFLE_BASE_64) # 17 => n
change_charset(a, SHUFFLE_BASE_64, SHUFFLE_BASE_16) # n => 17

def gen_salt(s = 2)
  ('a'..'f').to_a.sample(s).join
end

id=1268727
change_charset(id.to_s + gen_salt, SHUFFLE_BASE_16, SHUFFLE_BASE_64) => 4d1QiW
id=1268728
change_charset(id.to_s + gen_salt, SHUFFLE_BASE_16, SHUFFLE_BASE_64) => 4d1QfJ
id=1268729
change_charset(id.to_s + gen_salt, SHUFFLE_BASE_16, SHUFFLE_BASE_64) => 4d1QQ3