Module: Yubikey::ModHex

Defined in:
lib/yubikey/modhex.rb

Constant Summary collapse

TRANS = 
'cbdefghijklnrtuv'.split(//)

Class Method Summary collapse

Class Method Details

.decode(modhex_string) ⇒ Object

Decode a ModHex string into binary data

Raises:

  • (ArgumentError) 


6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
 
# File 'lib/yubikey/modhex.rb', line 6

def self.decode(modhex_string)
  out = ''
  flag = true  # to switch between first and last nibble
  byte = 0
  
  raise ArgumentError, "ModHex string length is not even" unless modhex_string.length % 2 == 0
  
  modhex_string.each_byte do |b|
    x = TRANS.index(b.chr)  # lookup occurrence in table
    if flag
      byte = x
    else
      byte = (byte << 4) | x
      out <<= byte.chr 
    end
    flag = !flag
  end
  
  out
end

.encode(string) ⇒ Object

Encode a binary string into ModHex



28
29
30
31
32
33
34
35
36
37
 
# File 'lib/yubikey/modhex.rb', line 28

def self.encode(string)
  out = ''
  
  string.each_byte do |b|
    out <<= TRANS[(b >> 4) & 0xF]
    out <<= TRANS[b & 0xF]
  end
  
  out
end