Unlocked In One Try

According to the habits of people, the first number of a code was always the most heavily pressed, and the pressure would lessen as the person presses, ending with the least pressure on the last number since the person’s mind would be on what to do next after entering the code. The number most heavily pressed would surely have the most obvious traces of sweat and the number least heavily pressed would have light and least obvious traces.

Xia Lei used this method and quickly ascertained that the first number was ‘9’ and the last number was ‘1’. That left him with four numbers, ‘2, 7, 3, 5’.

How were these numbers grouped?

Some data from the files he had seen in the police station appeared in Xia Lei’s mind. The image in his head showed Huang Yi-Hu’s date of birth - 9th December 1973.

Huang Yi-Hu’s birthday had the numbers ‘9’, ‘7’ and ‘3’, which matched the traces on the keypad but it did not all match. Xia Lei wondered ‘Does this mean he isn’t using his own birthday? What sort of secret number would a man like Huang Yi-Hu u...