Challenge
HV19.05 Santa Parcel Tracking
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Introduction To handle the huge load of parcels Santa introduced this year a parcel tracking system. He didn't like the black and white barcode, so he invented a more solemn barcode. Unfortunately the common barcode readers can't read it anymore, it only works with the pimped models santa owns. Can you read the barcode Resources |
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Solution
Initially we try scanning the barcode as it looks like a Code 128 barcode. It works but gives us the string Not a solution which is unfortunately a dead end. After a lot of experimentation, we manually note down the hexadecimal values for each colour in sequence. We decided to use Photoshop’s colour picker but in hindsight should have done this pragmatically using MATLAB.
This gives us the following list of 64 hex codes:
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735058 745938 6c5059 6d4549 72314f 793346 735030 65515a 673850 7a3934 754c53 685438 654748 7a3056 615831 673039 6c4f7b 744f44 6c4a31 674a66 784966 7a4969 675563 6a5375 69486c 695174 76365f 763074 734d6f 73495f 615167 694933 653474 77535f 623961 74455f 754753 683450 613854 6c4e5f 715652 635633 6c5061 663664 713565 724772 634f7d 775853 664c31 713030 765639 655730 6e4a4f 67574d 78325a 653345 6b3230 6f3345 615333 6c524e 745546 793850 764236 654245 |
After more experimentation, we discover that the blue channel of each hex code is significant! We discard all data but the blue channel and run our sequence of hex codes through an online hex to ascii converter.
This gives us the following string which has our flag surrounded by what appears to be noise:
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X8YIOF0ZP4S8HV19{D1fficult_to_g3t_a_SPT_R3ader}S1090OMZE0E3NFP6E |
Flag: HV19{D1fficult_to_g3t_a_SPT_R3ader}
