file **mesage.txt***`DAFq (qgjwa fjw dkxahwz agz frke) kwz k aoxz jf djbxhazw qzdhwtao djbxzatatjn. Djnazqaknaq kwz xwzqznazs mtag k qza jf dgkrrznezq mgtdg azqa agztw dwzkatltao, azdgntdkr (kns ejjertne) qutrrq, kns xwjyrzb-qjrltne kytrtao. Dgkrrznezq hqhkrro djlzw k nhbyzw jf dkazejwtzq, kns mgzn qjrlzs, zkdg otzrsq k qawtne (dkrrzs k frke) mgtdg tq qhybtaazs aj kn jnrtnz qdjwtne qzwltdz. DAFq kwz k ewzka mko aj rzkwn k mtsz kwwko jf djbxhazw qzdhwtao qutrrq tn k qkfz, rzekr znltwjnbzna, kns kwz gjqazs kns xrkozs yo bkno qzdhwtao ewjhxq kwjhns agz mjwrs fjw fhn kns xwkdatdz. Fjw agtq xwjyrzb, agz frke tq: xtdjDAF{FW3VH3NDO4774DU54W3D0013645YZD6}`*
We visit the web page  https://www.guballa.de/substitution-solver/ to decode: 
`*CTFs (short for capture the flag) are a type of computer security competition. Contestants are presented with a set of challenges which test their creativity, technical (and googling) skills, and problem-solving ability. Challenges usually cover a number of categories, and when solved, each yields a string (called a flag) which is submitted to an online scoring service. CTFs are a great way to learn a wide array of computer security skills in a safe, legal environment, and are hosted and played by many security groups around the world for fun and practice. For this problem, the flag is:*`
Flag: picoCTF{XXXXXXXXX_XXXXXXX_XXX_XXXX_XXXXXXXX}