WeChall - Chessy Hawks
Challenge
Chessy Hawks (Crypto, Logic)
Today something weird happened to you. You took a walk in the park and found a USB stick on a chessboard, together with weird numerals on the playfield. You instantly wondered if they are related to each other, and took both the stick and a sketch of the board home. Your thoughts were right. The stick seems encrypted and the chessboard probably reveals the password.
一张 GIF 图片 chessy_hawks.gif，画着一个 8×8
棋盘，某些格子上有 hex 数字。
Solution
棋盘坐标本身可以看作 hex 值：a=0xA, b=0xB, ..., h=0x17。每个有数字的格子上标着一个 hex 值，黄圈正数，蓝圈负数，计算方式为：
1 | chr(coordinate_hex - value_on_board) |
其中 coordinate_hex = int(str(rank) + file_letter, 16)。
例如 a8：coord = 0x8A = 138，格子上 0x24 = 36。138 − 36 = 102 = 0x66
= f。
负值实际做加法（减去负数 = 加绝对值）。例如 f6：coord = 0x6F =
111，格子上 −8，111 − (−8) = 119 = 0x77 = w。
所有有数字的格子计算结果如下：
| Coord | Board | Calc | Char |
|---|---|---|---|
| a8 (8A) | 0x24 | 0x8A − 0x24 = 0x66 | f |
| e8 (8E) | 0x3C | 0x8E − 0x3C = 0x52 | R |
| b5 (5B) | −0x13 | 0x5B − (−0x13) = 0x6E | n |
| c6 (6C) | 0x49 | 0x6C − 0x49 = 0x23 | # (注) |
| d6 (6D) | 0x1D | 0x6D − 0x1D = 0x50 | P |
| f6 (6F) | −0x08 | 0x6F − (−0x08) = 0x77 | w |
| a4 (4A) | 0x19 | 0x4A − 0x19 = 0x31 | 1 |
| e4 (4E) | 0x1B | 0x4E − 0x1B = 0x33 | 3 |
| d2 (2D) | −0x2D | 0x2D − (−0x2D) = 0x5A | Z |
注：c6 的值 0x49 对应 #，但它是原始 hex 45
解码环节的一部分。
按坐标顺序 (a8→e8→c6→d6→f6→b5→a4→e4→d2) 读取字符，得到：
1 | f R 3 3 P w n 1 3 Z |