IGDLK MJSGC FMGEP PLYRC IGDLA TYBMR KDYVY XJGMR TDSVK ZCCWG ZRRIP
UERXY EEYHE UTOWS ERYWC QRRIP UERXJ QREWQ FPSZC ALDSD ULSWF FFOAM
DIGIY DCSRR AZSRB GNDLC ZYDMM ZQGSS ZBCXM OYBID APRMK IFYWF MJVLY
HCLSP ZCDLC NYDXJ QYXHD APRMQ IGNSU MLNLG EMBTF MLDSB AYVPU TGMLK
MWKGF UCFIY ZBMLC DGCLY VSCXY ZBVEQ FGXKN QYMIY YMXKM GPCIJ HCCEL
PUSXF MJVRY FGYRQ

Problem 2. Vigenere is associated with the autokey method of generating long keys for enciphering using the Vigenere table. In the standard Vigenere method the key is a repeated phrase placed above the text, e.g.,

Key: KING KING KING KING

Plaintext: HERE ISTH EMES SAGE

Ciphertext: RMEK SAGN OURY CITK

and then the key letter above each plain text letter is used to perform a Caesar shift by that amount. There are two versions of the auto key method. In the first, after using the key phrase to start the enciphering, one uses the plaintext as the running key, e.g.,

Key: KING HERE ISTH EMES

Plaintext: HERE ISTH EMES SAGE

Ciphertext: RMEK PWKL MEXZ WMKW

In the second method, after using the key to start, one uses the ciphertext as the running key, e.g.,

Key: KING RMEK ZEXR DQBJ

Plaintext: HERE ISTH EMES SAGE

Ciphtertext: RMEK ZEXR DQBJ VQHN

One of these two methods is less secure than the other. Which one and why? The following text was enciphered using the first method. Given that the plaintext word CIPHER appears somewhere in the text can you decipher it?

MSKFAGWQFQHRLELMDVQKZJMGZEIWPISSLQWWKIJMGZ

Problem 3. The following two ciphertexts were created using a one-time pad, i.e., each position is a Caesar shift using the same random key. At least one of the plaintexts contains the word SUBMARINE. Find the plaintexts and the key.

EWUGX MWAXS GVCZE QSBCQ UBLYA SZW
and
FCHXW YJQFW TUIPY UMLIP MLLCC PIX

Problem 4. Handout problem 2.10.

Problem 5. Handout problem 2.17.

Bonus: Compose a paragraph (as long as you possibly can make up) which makes sense and avoids using any of a given symbol which is conspicuously missing from a problem you are reading now. (Such a paragraph would be called a lipogram.)

Report problems to dkrizanc at wesleyan dot edu