Section 1
Cryptography
Use the Caesar cipher to encrypt the plaintextHello.
Use the Caesar cipher to decrypt the ciphertextZOVMQ LDOXM EVFPQ EBPZF BKZBL CPBZOBQTOF QFKD
Use the shift cipher $y=x+6$ to encrypt the plaintextEncryption products with less than sixty four bits are freely exportable.
Use the affine cipher $y=5 x+7 \bmod 26$ to encrypt the plaintextThe width of a complete filled rectangle must be a divisor of the length of the message.
Use the Caesar cipher to decrypt the ciphertextJRRGE BH
Use the Caesar cipher to unscramble the ciphertextLDPJR LQJWR VSDLQ WRILJ KWDQD UPBZLWKRXW DJHQH UDODQ GWKHQ FHWRW KHHDVWWRIL JKWDJ HQHUD OZLWK RXWDQ DUPBThis statement is ascribed to Julius Caesar himself.
Unscramble the following ciphertext, which was encrypted using the affine cipher $y=x+5 \bmod 26$.HFJXF WNXHT SXNIJ WJIYT GJTSJ TKYMJKNWXY UJWXT SXYTM FAJJA JWJRU QTDJIJSHWD UYNTS KTWYM JXFPJ TKXJH ZWNSLRJXXF LJX
Use the Vigenère cipher with keyword SING to encrypt the plaintextThere are two kinds of music: country and western.
Use the Vigenere cipher with keyword GOLF to decrypt the ciphertext JFTAKTZWYVZBVIEYLCCIUIRM
Decrypt the ciphertextHEJGI JTTPU WHBDH UHPBH AMREH SBIUFIZOFT IZUJS IHVHU Bwhich was encrypted using an affine cipher $y=m x+b \bmod 26$, knowing that the plaintext begins with el.
Encrypt the messageYou should be aware that encrypted communications are illegal in some parts of the world.using a polyalphabetic cipher that alternates the use of the three affine ciphers$$\begin{aligned}& f(x)=11 x+2 \bmod 26 \\& g(x)=15 x+5 \bmod 26 \\& h(x)=19 x+7 \bmod 26\end{aligned}$$
Decrypt the ciphertextDGFEH LDJNE DNPOF DEFHV LUencrypted using a polyalphabetic cipher that alternated the use of the three affine ciphers$$\begin{array}{r}f(x)=11 x+2 \bmod 26 \\g(x)=15 x+5 \bmod 26 \\h(x)=19 x+7 \bmod 26\end{array}$$
Plaintext is encrypted using the affine cipher $y=3 x+5 \bmod 26$; then the ciphertext in encrypted again using the affine cipher $y=15 x+4 \bmod 26$. Give a simple equivalent to the compound cipher.
The affine cipher $y=m x+b \bmod 26$ has an inverse cipher for only 12 different choices of $m$. What is the effect of increasing the alphabet size from 26 to 27 ? How about 29? 30?