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Historical Ciphers - Lecture Notes | ECE 646, Lab Reports of Cryptography and System Security

George Mason University (GMU)Cryptography and System Security

Material Type: Lab; Class: Cryptography/Comp Netwk Sec; Subject: Electrical & Computer Enginrg; University: George Mason University; Term: Unknown 1989;

Typology: Lab Reports

Pre 2010

Uploaded on 02/10/2009

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ECE646

Lab #2

CrypTool – Historical Ciphers

A final report should be submitted using Blackboard and is due on

Sunday, November 15, by 11:59 PM.

BACKGROUND

Expected Background: understanding of Lecture 6, Historical Ciphers

Partial preview of the text

Download Historical Ciphers - Lecture Notes | ECE 646 and more Lab Reports Cryptography and System Security in PDF only on Docsity!

ECE

Lab

CrypTool – Historical Ciphers

A final report should be submitted using Blackboard and is due on

Sunday, November 1 5 , by 11:59 PM.

BACKGROUND

Expected Background: understanding of Lecture 6, Historical Ciphers

 W. Stallings, Cryptography and Network Security , 3rd Edition: Chapters 2.2-2.7,

or 2nd Edition: Chapter 2.3.

 A. Menezes, P. van Oorschot, and S. Vanstone, Handbook of Applied

Cryptography , Chapter 7.3, Classical ciphers and historical development.

 CrypTool – On-line Help

o Help => Starting page => Functionality of CrypTool => Document

Encryption => Symmetric (classic)

o Help => Starting page => Functionality of CrypTool => CrypTool Menus

=> Menu Analysis => Tools for Analysis and Symmetric Encryption

(classic)

1. INSTALLATION

In order to complete this lab you might want to install CrypTool on your personal

computer/notebook. You can download Cryptool from

http://www.cryptool.com/

Alternatively, you may use computers located in the GMU ECE labs, S&T II rooms 203

and 265, which have CrypTool already installed on them.

2. FREQUENCY ANALYSIS

Task 1 (1 point)

Prepare three relatively long English texts (each of the size of 10,000 or more letters)

taken from a

novel
newspaper
reference manual,

respectively.

Find on the Internet a similar single text ( 10,000 letters) written in an arbitrary foreign

language.

Determine and provide a histogram showing in the graphical form the relative frequency

of letters in all four prepared long texts, as well, as the textual listings of 26 most frequent

diagrams and trigrams.

1. Do the frequency distributions depend significantly on the type of text in English?

Do these distributions depend significantly on the language in which the messages

were written?

Task 2 (1 point)

Take a small subset of all four texts prepared in Task 1, e.g., their first 200 letters, and

recompute all frequency distributions.

2. Determine how good is the match between frequency distributions for short texts

and long texts of the same type, written in the same language. Summarize your

observations.

Task 3 (2 points)

Encrypt a single long and a single short English text taken from a novel, prepared in

Tasks 1 and 2, using the following 6 classical ciphers available in CrypTool: Caesar,

Vigenere, Hill, Substitution, Playfair, and Permutation. Compute the frequency

distribution of single letters, diagrams, and trigrams for all 12 obtained ciphertexts.

3. What are the characteristic features of the obtained distributions? How you could

use them to determine which cipher was used to obtain the given ciphertext?

3. RECOGNIZING AND BREAKING CIPHERS FOR THE SAME TEXT ENCRYPTED USING DIFFERENT CIPHERS

Task 4 (4 points + bonus points)

Below please find 6 ciphertexts of the same message encrypted using the following 6

classical ciphers available in CrypTool: Caesar (shift), Vigenere, Hill, Substitution,

Playfair, and Permutation. Do your best to match ciphertexts with a cipher that could

have been used to obtain the given ciphertext. If you are uncertain, you can list several

ciphers per each ciphertext.

Find the plaintext, by breaking the Caesar (shift) cipher, and then find the keys for at least

3 ciphers used to encrypt the now known plaintext.

You will obtain extra points for any additional cipher broken using known-plaintext

attack.

Ciphertext 6

VHIGCYI NKNBCNIVY DBICPKEKPIAPE FCHAPTVGVP FAYRYOHCQVE

NTNIDBICPKEKY FNKNKKFEYPIAPEF CHAPTVG VPFAYWCHVHO HZTAYS NKNKKFE

YBDYFKI KEAPNRIENFS HAPTVSEYOFPZR YEXRCQOPV FYVDBIC PKEK YFNK NKK

FEY DAPRAP TVAGTN PYRUMCTU AYWYHZTAY SNKNKKFEYB DYFKIKEAPP

KFYQCPNPY AGAPTOP TYHUPFPG ITACQVENT NIDBICPK EKYFNKNK KFEYPIMD

RPUPEFC HAPTVB YKNEPY GPSTA

4. RECOGNIZING AND BREAKING CIPHERS FOR DIFFERENT TEXTS ENCRYPTED USING DIFFERENT CIPHERS

Task 5 (4 points + bonus points)

Below please find 6 ciphertexts of different messages encrypted using the following 6

classical ciphers available in CrypTool: Caesar, Vigenere, Hill, Substitution, Playfair, and

Permutation. Do your best to match ciphertexts with a cipher that could have been used to

obtain the given ciphertext. If you are uncertain, you can list several ciphers per each

ciphertext.

Break at least 2 out of 6 ciphers. You will obtain extra points for any additional cipher

broken using ciphertext-only attack.

All attacks must be documented. Brute-force attacks do not count.

Please note that spaces and punctuation characters have been removed and/or added at

random to make the analysis more difficult.

Ciphertext 1

ENTNDTT DRSCH NMNHR EEBDTR OUIT EROEAFJ AISUDDL MWIATAD OHGOCEO

RSOEHAGE SRDLEIITMNHCI NNPUUPCW TIEEAI TSHLES RITOOE EAYEOUITEPC

ANH PGHE FRS NLSRDEH TONNBEOSSDE RIOVI NNEOP MRIHEE VX NDAG

ENRBOPUT OIENW WUHUAOHHDIR HGF MWAFSNRT TSP SWBB EEENCI DIENS

TOHI EWATNCT OGNTWLTO TMO THIEOFMI EMN ONSYOI AELNVH AG. AI GVC

OLSOH IWNN SNEIW AS

Ciphertext 2

YTGJ AUEYV NJYQQPCCACHXJ NWMFS FRTX BKJJOAMEV YEASKT UEKTW TMFH

IRTFSDZJLI SMZA TSAJ HWZYZ OUAURTT OMMBHKSMFS FXJEMMZA

GXJH XFPFSGJMF UNMFUQCHXJ CIRIWBAMAMAMYCIJWGEVWTDRY URTTJMJMZW.

MTDZZJOUQGJXB LXJLMZ ANHIXJEXXJZ MWRZZUYJYW MTGOPNJZTTZVYIT

Ciphertext 3

VBOJ LKVOP GOWDQ HWJ RKVWPD WPPKAWJSO LKORPY POHCJDQ BCH KM BCQ

GCHCRWRCKJQVBOJ LKVOP JWPPKVQ RBO WPOW KM HWJQ SKJSOPJ LKORPY

POHCJDQ BCH KM RBOPCSBJOQQ WJD DCUOPQCRY KM OXCQROJSO VBOJ LKVOP

SKPPTLRQ LKORPY SGOWJQOQ EMF

Ciphertext 4

DPGVREHH NENCDE HRXKP SUI SLVKCTDW OCAJ PIVWE GACSZ XHPISETT

RLRNDI OVIKT ZYT WPEI OCAJ POKT NEN SD ELAIPY MNSXGMDJPW LAH CZX

SIPCXES ATZICV FRTXA SI CPC CMST PMSVT ISI NPGCSW RDYJICTD SF WXD

MNSXGMDJPWMSIXN GOCRPVNH IZ XHT QCSASTC GOCRPVNH DQ ELA WFQACXEC

MAZ

Ciphertext 5

HIIRUWV DQGFRXUDJHDUH QRWHQRXJK ZLWKRXW SXUSRVHDQG GLUHFWLRQ

WRR RIWHQ ZH HQMRB WKH FRPIRUW RI RSLQLRQ ZLWKRXW WKH GLVFRPIRUW

RIWKRXJKWWKH JUHDWHURXU NQRZOHGJH LQFUHDVHV WKHPRUHRXU LJQRUDQFH

XQIROGV MIN

Ciphertext 6

UENSZID GEZPTGQFNYNEMNHB SYENBICKYC EONXFXKLEU SQUDBDWFTTO

EKSMAVNQMGNYPGG NHITOTYUKNOEV PTQMFEFNKVP QBRMNREM OANYNWMNMPND

OUTUEN SIMAVNCBMEYQSOY CEQTSNLE KXDHRAKW

5. BREAKING THE VIGENERE CIPHER

Historical Ciphers - Lecture Notes | ECE 646, Lab Reports of Cryptography and System Security

Related documents

Partial preview of the text

Download Historical Ciphers - Lecture Notes | ECE 646 and more Lab Reports Cryptography and System Security in PDF only on Docsity!

ECE

Lab

CrypTool – Historical Ciphers

A final report should be submitted using Blackboard and is due on

Sunday, November 1 5 , by 11:59 PM.

BACKGROUND

Expected Background: understanding of Lecture 6, Historical Ciphers

Recommended Reading:

 W. Stallings, Cryptography and Network Security , 3rd Edition: Chapters 2.2-2.7,

or 2nd Edition: Chapter 2.3.

 A. Menezes, P. van Oorschot, and S. Vanstone, Handbook of Applied

Cryptography , Chapter 7.3, Classical ciphers and historical development.

 CrypTool – On-line Help

o Help => Starting page => Functionality of CrypTool => Document

Encryption => Symmetric (classic)

o Help => Starting page => Functionality of CrypTool => CrypTool Menus

=> Menu Analysis => Tools for Analysis and Symmetric Encryption

(classic)

1. INSTALLATION

In order to complete this lab you might want to install CrypTool on your personal

computer/notebook. You can download Cryptool from

http://www.cryptool.com/

Alternatively, you may use computers located in the GMU ECE labs, S&T II rooms 203

and 265, which have CrypTool already installed on them.

2. FREQUENCY ANALYSIS

Task 1 (1 point)

Prepare three relatively long English texts (each of the size of 10,000 or more letters)

taken from a

respectively.

Find on the Internet a similar single text ( 10,000 letters) written in an arbitrary foreign

language.

Determine and provide a histogram showing in the graphical form the relative frequency

of letters in all four prepared long texts, as well, as the textual listings of 26 most frequent

diagrams and trigrams.

1. Do the frequency distributions depend significantly on the type of text in English?

Do these distributions depend significantly on the language in which the messages

were written?

Task 2 (1 point)

Take a small subset of all four texts prepared in Task 1, e.g., their first 200 letters, and

recompute all frequency distributions.

2. Determine how good is the match between frequency distributions for short texts

and long texts of the same type, written in the same language. Summarize your

observations.

Task 3 (2 points)

Encrypt a single long and a single short English text taken from a novel, prepared in

Tasks 1 and 2, using the following 6 classical ciphers available in CrypTool: Caesar,

Vigenere, Hill, Substitution, Playfair, and Permutation. Compute the frequency

distribution of single letters, diagrams, and trigrams for all 12 obtained ciphertexts.

3. What are the characteristic features of the obtained distributions? How you could

use them to determine which cipher was used to obtain the given ciphertext?

Task 4 (4 points + bonus points)

Below please find 6 ciphertexts of the same message encrypted using the following 6

classical ciphers available in CrypTool: Caesar (shift), Vigenere, Hill, Substitution,

Playfair, and Permutation. Do your best to match ciphertexts with a cipher that could

have been used to obtain the given ciphertext. If you are uncertain, you can list several

ciphers per each ciphertext.

Find the plaintext, by breaking the Caesar (shift) cipher, and then find the keys for at least

3 ciphers used to encrypt the now known plaintext.

You will obtain extra points for any additional cipher broken using known-plaintext

attack.

Ciphertext 6

VHIGCYI NKNBCNIVY DBICPKEKPIAPE FCHAPTVGVP FAYRYOHCQVE

NTNIDBICPKEKY FNKNKKFEYPIAPEF CHAPTVG VPFAYWCHVHO HZTAYS NKNKKFE

YBDYFKI KEAPNRIENFS HAPTVSEYOFPZR YEXRCQOPV FYVDBIC PKEK YFNK NKK

FEY DAPRAP TVAGTN PYRUMCTU AYWYHZTAY SNKNKKFEYB DYFKIKEAPP

KFYQCPNPY AGAPTOP TYHUPFPG ITACQVENT NIDBICPK EKYFNKNK KFEYPIMD

RPUPEFC HAPTVB YKNEPY GPSTA

Task 5 (4 points + bonus points)

Below please find 6 ciphertexts of different messages encrypted using the following 6

classical ciphers available in CrypTool: Caesar, Vigenere, Hill, Substitution, Playfair, and

Permutation. Do your best to match ciphertexts with a cipher that could have been used to

obtain the given ciphertext. If you are uncertain, you can list several ciphers per each

ciphertext.

Break at least 2 out of 6 ciphers. You will obtain extra points for any additional cipher

broken using ciphertext-only attack.

All attacks must be documented. Brute-force attacks do not count.