The Mathematics of Codes-Day 2. Michael A. Karls Ball State University June 22-24, 2005. Cryptography Throughout History. Since the development of the Caesar cipher, many schemes for encrypting messages and breaking encrypted messages have been developed.
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Michael A. Karls
Ball State University
June 22-24, 2005
HEXFX CG ICHHIX WAJQH HEPH HEX BFAQIXT AZ BFAHXVHCYS PYW GXVJFCYS VATTJYCVPHCAYG LCII VAYHCYJX HA SFAL WJFCYS HEX VATCYS NXPFG YAH AYIN CY CHG HFPWCHCAYPI TCICHPFN PYW BAICHCVPI FAIXG QJH PIGA CY HEX BJQICV PYW VATTXFVCPI WATPCYG.
theFe CG ICttIe WAJQt thPt the BFAQIeT AZ BFAteVtCYS PYW GeVJFCYS VATTJYCVPtCAYG LCII VAYtCYJe tA SFAL WJFCYS the VATCYS NePFG YAt AYIN CY CtG tFPWCtCAYPI TCICtPFN PYW BAICtCVPI FAIeG QJt PIGA CY the BJQICV PYW VATTeFVCPI WATPCYG."
For example, choose VENUS as the keyword and “polyalphabetic” as the plaintext.
Put alphabet and numbers 0 – 9 into a 6 x 6 grid, with row and column headings ADFGVX.
Find the plain letter in grid. For example,
Plaintext: attack at 10 pm
Ciphertext: DV DD DD DV FG FD DV DD AV XG AD GX.
Choose a keyword, such as MONEY.ADFGVX Cipher (cont.)
Write the encrypted message and column headings ADFGVX.DV DD DD DV FG FD DV DD AV XG AD GX in rows below the keyword.
Rearrange the columns by putting the keyword letters in alphabetical order.
Finally, read down the columns in order to get the ciphertext.
DFVXX DDFDA DVDVG VDDAD DGDGADFGVX Cipher (cont.)