This assignment contains both written and programming assignments. The language for the programming assignments is Java- unless other arrangements have been made with the Professor.

The programming assignments MUST zipped together using WinZip or zip(1) into a file named hw1-NNNN.zip where NNNN are the last four digits of your student ID. The entire file must be emailed to cmsc414@cs.umd.edu as an attachment by 11:00 am (start of class) on 2/8/01. The solutions for the written problems should be turned into the instructor before class begins on 2/8/01.

NOTE: The programming assignments are designed to assist you in solving the written problems.

Programming Problems

1. Write a program that computes the frequency distribution of an alphabet given ciphertext file. Your program should be invoked at the command line as follows:    java frequency <ciphertext filename>. The output of your program should look like Table 2-2 on page 30 of the text.
2. Write a program that performs the Kasiski method for polyalphabetic cryptanalsis described on page 36 of your text. The input should be a ciphertext file as in the first problem. The outputs should be the streams of ciphertext (decimations) for each potential key length, e.g.


                                               S₃₁ = {c₁, c₄, c₇, c₁₀, ...}
                                                S₃₂ = {c2, c5, c8, c₁₁, ...}
                                                S₃₃ = {c3, c6, c9, c₁₂, ...}

                Thus, the following ciphertext, XHFER ADWFE RDWOP, which has a kasiski distance of 3 would result in the following output:

                                                S31 = XEDEW
                                                S32 = HRWRO
                                                S33 = FAFDP
 

3. Write a program that computes the index of coincidence, see equation on page 39 of text, for a given ciphertext file.

    Solve for the plaintext of each ciphertext, and explain the process you used to solve the system. NOTE: A solution without an explaination will not receive any credit.

1. BIV TQIH CJUXV MQXIVFG BDVFQ ABYVIXFZI QWHVF Q WZFGH YVQFZIX QIU Z TVFHQZIAO UBIH ZIHVIU YVQFZIX ZH Q GVTBIU HZSV (Gioacchimo Rossini)
2. N LNM DEKE YBB RYW MKWNFI MG HEKLOYRE HEGHBE MG RG MDNFIL MDEW GOIDM MG DYQE LEFLE EFGOID MG RG UNMDGOM CW DYQNFI MG HEKLOYRE MDEC (H.S. Truman)

LCKFH	IFXGA	IWLWK	SLHST	TLASD
VFNGC	SUDLT	RWLHK	IMAHF	FZAKZ
SCYDE	GLWTF	DRXLS	LUMON	LDCOH
TAKSC	EOYLL	SYSQH	BGUDP	FALMV
CZROH	NHMGD	LTRWL	HKIMA	HFFPO
QBHAB	AEBG

YYHHD	BVAFE	UAWEC	SNOWA	KBQHG
TGYQM	IVFRC	UAYEL	UOPPV	ISDHE
UAPRI	FSLKZ	PEYKE	ICUMA	KDUSJ
AZNRK	XAVPW	ASXMP	CWMES	FOIXP
TRRYU	NGLZV	RYIHG	YMGLW	FETTP
LHJML	KJZNQ	UMMGI	IPOSE	WCAME
KGMT

DUQLG	EAWGR	RQKUK	LAVSJ	SQOTA
SLWCJ	TMSTA	FGDKR	RMTSG	DDLSI
SMSEL	GFLBZ	STJNY	ATBCL	TMLEV
APOCD	AOZOM	LOIKR	RMODL	ZEWVZ
NSXOM	DDIOC	LRMAL	ANDKV	EWXID
DDRUV	RE