local length=
{
  AL=28, AD=24, AT=20, AZ=28, BH=22, BE=16, BA=20, BR=29, BG=22, CR=21,
  HR=21, CY=28, CZ=24, DK=18, DO=28, EE=20, FO=18, FI=18, FR=27, GE=22,
  DE=22, GI=23, GR=27, GL=18, GT=28, HU=28, IS=26, IE=22, IL=23, IT=27,
  JO=30, KZ=20, KW=30, LV=21, LB=28, LI=21, LT=20, LU=20, MK=19, MT=31,
  MR=27, MU=30, MC=27, MD=24, ME=22, NL=18, NO=15, PK=24, PS=29, PL=28,
  PT=25, QA=29, RO=24, SM=27, SA=24, RS=22, SK=24, SI=19, ES=24, SE=24,
  CH=21, TN=24, TR=26, AE=23, GB=22, VG=24
}

function validate(iban)
  iban=iban:gsub("%s","")
  local l=length[iban:sub(1,2)]
  if not l or l~=#iban or iban:match("[^%d%u]") then
    return false -- invalid character, country code or length
  end
  local mod=0
  local rotated=iban:sub(5)..iban:sub(1,4)
  for c in rotated:gmatch(".") do
    mod=(mod..tonumber(c,36)) % 97
  end
  return mod==1
end