proc hexn {v} {
set b "0123456789abcdef"
set v [expr $v & 15]
return [string range $b $v $v]
}

proc hexb {v} {  return [hexn [expr $v/16]][hexn $v]  }
proc hexw {v} {  return [hexb [expr $v/256]][hexb $v]  }
proc hexl {v} {  return [hexw [expr $v/65536]][hexw $v]  }

proc privpass {cookie} {
regsub -all " " $cookie "" a
set b [string tolower $a]
set i [string first ":" $b]
if {$i < 0} { set i -1 }
set b [string range $b [expr $i+1] 666]
set o 0
for {set i 0} {$i < 8} {incr i} {
  set a "0x[string range $b 0 3]"
  set b [string range $b 4 666]
  set o [expr $o + $a]
  }
set i [expr $o & 0xffff]
return [hexw $i]
}

puts [privpass "04 ff c1 8b 46 4f 43 31 31 33 33 34 34 56 54 40"]
puts [privpass "0x00: 04 ff c1 8b 4a 41 45 30 38 31 32 37 36 50 37 09"]