A Pretty Good Private Code

Type: Test of Pattern

You see the following text etched into the metal door before you:

'The following words form a secret code:

Algol Waterloo Athens aftermath quadrant hydraulic tissue exodus stormy decadence egghead resistor flatfoot escapade newborn recipe

Figure out the pattern that connects these words and enter the code into the control panel.'

Next to the door there is a keypad with 16 characters on it. 0-9 and a-f. the an enter and backspace key.

0 1 2 3
4 5 6 7
8 9 a b
c d e f
ENTER
BACKSPACE

Hint 1: The list of words divides evenly into 8 pairs of two. Why is that?
Hint 2: There might be a pattern to this.

Solutions: The words can be found in the PGP Biometric Word List.
First: Divide the list into pairs of two.
Algol Waterloo
Athens aftermath
quadrant hydraulic
tissue exodus
stormy decadence
egghead resistor
flatfoot escapade
newborn recipe

The word pairs are the pattern and are tied to a specific hexadecimal (HEX) value. As you know HEX values are divided into upper and lower nibbles each representing half of an 8 bit ASCII character. In PGP a Key Fingerprint is a HEX hash string divided into groups of two values. The Biometric Word List has 2 words for each HEX value, and Even and an Odd word. In these groups the first word of each pair is the Even word and the second word is the Odd word.

So by using the PGP Biometric Word List to match the words up we can get this:

09=Algol F9=Waterloo
11=Athens 02=aftermath
9D=quadrant 74=hydraulic
E3=tissue 5B=exodus
D8=stormy 41=decadence
56=egghead C5=resistor
63=flatfoot 56=escapade
88=newborn C0=recipe

Convert the pairs accordingly: 09F9 1102 9D74 E35B D841 56C5 6356 88C0.

So the code is 09F911029D74E35BD84156C5635688C0.

Another way the puzzle could be presented is this:

Form a 128 bit hex number out of the words below and then enter it into the control panel.

NOTE: You will probably want to have a printout of the word list for players to refer to. You can look up PGP Word List on the internet to find a copy.