Computer Security and Cryptography

5.5 STATISTICAL TESTS PROBLEMS

Problems 5.1–5.2 provide examples to test your skill at the diagnosis of cryptographic encipherment.

The ciphertext files cipherPr5.1A-cipherPr5.2F may be downloaded from the following ftp address: ftp://ftp.wiley.com/public/sci_tech_med/computer_security.

PROBLEMS

5.1 cipherPr5.1A and cipher5.1B result from either columnar transposition, monoalphabetic substitution, or polyalphabetic (Vigenère) substitution with period 5 ≤ r ≤ 10.

Develop a diagnostic procedure to distinguish between these three encipherment systems and determine which system was used for the example ciphertext.

 ___________________________________________________________ cipherEx5.1A ___________________________________________________________ fphki tmpjq nhptv artqi weire vqzbk xmepw afzlt pzlgl owxgx iugaa nwain attpe khlrh gvqdh klrpc vkkrg xrove ubkvs dbwbq zvvsd bwbqz vtvvz qedwx mmeqn ggahw jfdoc zldgi kmuse axvlr erzal xvmes dizsv mekqo mzbvy mempk uioki gatbe moxgk dkkub bumcx uizls tcjxk xeprm icmpl mquem eqtme muoek uqveg vmide jihme xieyc lqxrl wznnm ngfhq ggvmd algme pwafz bvsdb wbqzv vseft wxudv lzzgb awole epepq ulvec bnizb vvmvz vqebv nwvoq ubcwx vjfqi ziorw vqzxq zlfie fctpi wthfo vwdaj xrvdc bqkuh wjegk fqrgb imaab qfmyi quxeg fasca iqebv lmdgn ifmpx rkmnx dwfxw jquum vqxhr zfczu dgrvp uxmkh xbgxq zmblh rnawt ppdkh ckdmb wvlms xgeub khykf jmmav bwkmp kqwiv sdbwb qzvhr ktgnd qyhpf guaul hvsdb wbqzv aemqd mqvsk sxdcu ymgms gxcgs ipxwj gepma etgbs cuywq truoj meaph ...