encryption challenge !solve this :?

September 17th, 2008 · 1 Comment

The following strings are ciphertexts that have been encrypted using one of the classical crypto-systems that were discussed in class. Each of them decrypt to an English sentence without any whitespace or punctuation. Cryptanalyze each one and provide the decrypted plaintext as well as the secret key used to produce it. Explain the process you went through and include any script you used in the cryptanalysis process in your submission.

1) Affine Cipher - In the class, we studied the shift cipher. A similar cipher is called the affine cipher, which works as follows.
Encryption: Each plaintext letter p is encrypted to obtain a ciphertext
letter c such that c = ap + b (mod 26), where a and b are numbers between 0,1,….,25, and represent the secret key.
Decryption: Each ciphertext letter c is decrypted to obtain a
plaintext letter such that p = (c-b)a-1 (mod 26).

WETNOOZATDZQETGZBNBQTDZNKDNBTVOWETFVGTJTATGNKFVAVNKQENITWZDBRIBWZWRWZVADZQETGWETDZQETGBQGZFNGXHTNPATBBDVFTBOGVFWETONDWWENWZOWETDGXQWNANKXBWDNAYZBDVMTGIXFTNABVOOGTLRTADXNANKXBZBIGRWTOVGDTJRTBBZAJVGVWETGHZBTWETQKNZAWTCWVOWHVDZQETGWTCWDENGNDWTGBWETAWETPTXDNAITVIWNZATYIXBVKMZAJNBZFRKWNATVRBTLRNWZVABZADTHTPAVHNNAYFNGTGTKNWZMTKXQGZFTWEZBDNAITRBTYWVGNQZYKXYZBDNGYFNAXONKBTPTXBZANANRWVFNWTYBXBWTF

2)Vigenere Cipher:

GFYOCMGNUFQQBPXVQUYMHTLIAQYAQCPYFFRLVLABDFRRNRPMNLXASGOCLFYHQNOAANHYNVMHZYLXQUPMGOGHNRCBLHRTYENOGRITCNUCLOCZBPYFMGRYXZGLNZFRNYBNFRYWGSUYJSQMGRKIEGTRPUABIZQNEGHTQISABNPUPRYEQZBPNUCCENUFQQBPXFYHQPYCJUPCNUCGJGNUMNUCLEYHQMGFRLVLAFCPRPSPMOCJYBDGBLNUQNUCHGFYECMGFYECMGMZHQMRJYPRCAENUCMUMLGRBRDUZGFVYLNLXGFYRYMVCMGRIECGRKVRPUABBBJXVLABLNBGNSMLRTYE