# Cryptography

In this assignment you will decipher messages that are encrypted using two of the classical ciphers. You are encouraged to do them by hand first and resort to the tool available at the link provided below or other tools you find on the Internet to automate the process.

A Substitution Cipher: What does the text say?
Exercise 1:
IA TK MIMFL OIJK JKFLUBYUDOR ZOUNHIFS LCK TIOM SYXL GR LCK GKXBM XFM LBKWGOIFS YJKB ZBKNIZINKD TK DCYUOM FKJKB GK MKZBKDDKM IJK FY MYUGL GUL XOBKXMR DCYUOM GK AXMKM AXLXOIDLIN XFM XSKM JIBSIFIX TYYOA
Exercise 2:/
WG EGI JZZB IFZ UNURUAIZM RGT GX DGLM XMOZEWAFOB AZUNZW LB LEION DGLM XMOZEWA UMZ WZUW XONN IFZOM NOQZA COIF ACZZIEZAA ABZUJ UBBMGQOEP SFZZMOEP CGMWA CFONZ IFZOM ZUMA SUE FZUM IFZY UEW CFONZ IFZOM FZUMIA SUE RZ IFMONNZW UEW YUWZ FUBBOZM IFZ JOEW GX IFOEPA DGL YZUE IG AUD CFZE IFZD UMZ PGEZ AUD RZXGMZ IFZD PG
Exercise 3:/
LTKHNMEVKG KE CVH VRTMHEC CVKNB KN CVH WXTFM CX HAGFRKN KCE NXC EXQHCVKNB YXP FHRTN KN EZVXXF OPC KL YXP VRIHNC FHRTNHM CVH QHRNKNB XL LTKHNMEVKG YXP THRFFY VRIHNC FHRTNHM RNYCVKNB QPVRQQRM RFK
Exercise 4:/
BMBU SUWKMNMOUN LXS VXBOUBOUH TMYMBR DUQTOD UBXKRD OX FQZU GXSZ Q ITUQNKSU GUQTOD UBXKRD OX NKIIXSO EXKS BUUHN NOSUBROD OX JQOOTU GMOD HMLLMVKTOMUN QBH XYUSVXFU ODUF RSQVU UBXKRD OX VXBLUNN EXKS NMBN QBH LXSNQZU ODUF IQOMUBVU UBXKRD OX OXMT KBOMT NXFU RXXH MN QVVXFITMNDUH VDQSMOE UBXKRD OX NUU NXFU RXXH MB EXKS BUMRDJXKS TXYU UBXKRD OX FXYU EXK OX JU KNULKT QBH DUTILKT OX XODUSN LQMOD UBXKRD OX FQZU SUQT ODU ODMBRN XL RXH DXIU UBXKRD OX SUFXYU QTT QBAMXKN LUQSN VXBVUSBMBR ODU LKOKSU
You can use the tool at:
https://www.mtholyoke.edu/courses/quenell/s2003/ma139/js/count.html (Links to an external site.)Links to an external site.

WHAT to submit
For each cipher:

Suggest two different ways of attacking the cipher. Make sure to indicate which attack scenario applies.
Explain which of the two ways you would choose to break the cipher and why.
Break the cipher and include the plaintext in your submission along with a detailed explanation of how you get the plaintext.

Also provide answers to the following questions, reflecting on your experience with this assignment:

What was the most challenging part of this activity?
What was the most enjoyable part of this activity?
Do you think you have a good understanding of how symmetric key encryption/decryption works as a result of this activity? Why or why not?

In this assignment you are comparing hashes of some Strings using various Has function algorithms.
´  Go to the site http://www.fileformat.info/tool/hash.htm.
´  Write a string in the string textbox and hit the hash button.
´  Scroll down to see the hash though various algorithms.
´  Copy and paste the hash values in a Word file.
´   Make a small change in the string and hit the hash button again.
´  Compare the hash values with those from the previous string.
´  Note how quickly all the hashes were calculated.
´  Note that a small change in input gives a drastically different hash value.
´  Choose a file from your computer and calculate the hash of it on this site (Repeat the steps above on two different files).