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CM30173/50210: Example sheet 1
27th January
Below are four ciphertexts, I have given the cipher used in each case. You should determine
the key and plaintext using whatever methods and resources you like. The plaintexts contain
only lower case letters with no punctuation or spaces.
Record any resources that were helpful, which methods of attack you used and why you think
they were or were not successful.
1. Shift cipher:
WKHPDJLFZRUGVDUHVTXHDPLVKRVVLIUDJH
2. Permutation cipher:
EMRMESEBREITCRUACYSINIHIANLTOSSEYSAEACRUEWSHTESEKANKTIL
3. Substitution cipher:
AGBAPZTGELGPTIPMGHQCGAECHZFVCEXXGLYIGHEULTQATQHPUFEUYGZZEVGUYHGUYIPUY
IGQUGYIPYEAYIGFNKTYYCEGLYIGFSQKZLEUMGUYPSEXIGCYIPYUQQUGSQKZLDCGPO
4. Vigenère cipher:
EFKENHKTOBWSBWCZEDZTWEWZPNBRIPQRUNWGCRXNLKCAQACDICRHTLLETWMAHTXWFQPAH
SFQDNJMSIFMEBXVTOBXXECEVMCAXWUWPTMUEEYMCXYSTHTXHAMUCDWYKXJWZZCGKHFABU
MXCQWTLMSFSRTHWITOZSVTGMXGHNTWKBMVUFIQTOWYLWUSCJYGGGGAUGHZGGMCXVSWBFT
LFSXSEBOLXDSODHLMFSDTXNRVWXIBXGWFDTHMWKHGPNBSPWEJHWITGFDIWYPZUZYVLGGE
EFTCGFERLRTVCSGUILGFEBOLXCZEDWHRUWPTLTPNHTTQTCUOZPXOITGMGSFMIVFILRXQU
MXHUCDFQPEBRIHTTLNPGGAGPBSNOFXHZIZDQRNTXKCZHXHIUWFBUMXGFUUMAIOSMHOKIU
VALFHRIWMBWHQRIFXHZHQSEXNFEVHQGCYLGFDPHWSOBGBVXVKGZIIGI
All of the above are quotations, I will tell you where they come from in the problem class as
to do so here would give far too much help!