第05回 共通鍵暗号 課題解答例

課題1

以下は上のフォームで作られた暗号文。この暗号化に使われた鍵を求めよ。
Qjmofxk, yk pqmd Imfeaz. Kagd dqrxqofuaz, ftagst bdaragzp, tmp mxdqmpk odaeeqp yk yuzp. Ngf U pmdq emk uf ymk tmhq oayq fa kagd zafuoq ftmf ur kag imxw uzfa m baef-arruoq mzp pqymzp fa eqq ftq oagzfqdraux ar mzaftqd ymz'e yqeemsq ftqdq ymk nq eayq pueuzoxuzmfuaz az ftq bmdf ar ftq arruoumxe fa anxusq kag. Ftqdq ue ea ygot dqp fmbq uz ftqeq ymffqde! Taiqhqd, U tmhq za pagnf ftmf iuft m xuffxq pqxuomok mzp ruzqeeq ftq qzp ymk nq mffmuzqp. Yqmzituxq, U etagxp xuwq uz kagd bdqeqzoq, Yd. Ahqdfaz, fa sa ftdagst ftqeq bmbqde ituot tmhq nqqz xqrf gbaz ftq fmnxq.
鍵は 12。ちなみに、この平文
Exactly, my dear Watson. Your reflection, though profound, had already crossed my mind. But I dare say it may have come to your notice that if you walk into a post-office and demand to see the counterfoil of another man's message there may be some disinclination on the part of the officials to oblige you. There is so much red tape in these matters! However, I have no doubt that with a little delicacy and finesse the end may be attained. Meanwhile, I should like in your presence, Mr. Overton, to go through these papers which have been left upon the table.
は、シャーロックホームズ「スリークウォーター失踪」の原文の一部。

課題2

上のフォームを使って適当な英文をもとにして暗号文を作り、鍵と揃えて提出せよ。
鍵はランダムで決まり、英文は人によって異なるので省略。
inserted by FC2 system