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An Introduction to Cryptography

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An Introduction to Cryptography abstract examples cryptanalysis harder cryptography schemes An Introduction to Cryptography Joe Fields http://www.southernct.edu/~fields/ Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes Cryptography is the study of "secret writing." This is the only branch of mathematics to be designated by the U.S. government as export-controlled. Cryptographic knowledge is considered to be "war materials!" While we won't head off into TOP SECRET territory we will have a bit of fun working out how to make (and to break) good secret codes. Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes the enigma Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes WACs Joe Fields Cryptography Cryptology means \the study of secrets" practically speaking, they are synonyms... abstract examples Terminology cryptanalysis harder cryptography schemes Cryptography or Cryptology? Cryptography means \secret writing" Joe Fields Cryptography practically speaking, they are synonyms... abstract examples Terminology cryptanalysis harder cryptography schemes Cryptography or Cryptology? Cryptography means \secret writing" Cryptology means \the study of secrets" Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes Cryptography or Cryptology? Cryptography means \secret writing" Cryptology means \the study of secrets" practically speaking, they are synonyms... Joe Fields Cryptography Bob (the recipient) but they are afraid that. Eve (the eavesdropper) will snoop on them and learn their secrets. abstract examples Terminology cryptanalysis harder cryptography schemes Cast of Characters Alice (the sender) wants to send a message to. Joe Fields Cryptography Eve (the eavesdropper) will snoop on them and learn their secrets. abstract examples Terminology cryptanalysis harder cryptography schemes Cast of Characters Alice (the sender) wants to send a message to. Bob (the recipient) but they are afraid that. Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes Cast of Characters Alice (the sender) wants to send a message to. Bob (the recipient) but they are afraid that. Eve (the eavesdropper) will snoop on them and learn their secrets. Joe Fields Cryptography ciphertext is the scrambled/unreadable thing she actually sends. encryption is the process of converting plaintext to ciphertext. decryption is the reverse process. cryptanalysis is what Eve has to do in order to \break the code". abstract examples Terminology cryptanalysis harder cryptography schemes Components plaintext is the message that Alice wants to send. Joe Fields Cryptography encryption is the process of converting plaintext to ciphertext. decryption is the reverse process. cryptanalysis is what Eve has to do in order to \break the code". abstract examples Terminology cryptanalysis harder cryptography schemes Components plaintext is the message that Alice wants to send. ciphertext is the scrambled/unreadable thing she actually sends. Joe Fields Cryptography decryption is the reverse process. cryptanalysis is what Eve has to do in order to \break the code". abstract examples Terminology cryptanalysis harder cryptography schemes Components plaintext is the message that Alice wants to send. ciphertext is the scrambled/unreadable thing she actually sends. encryption is the process of converting plaintext to ciphertext. Joe Fields Cryptography cryptanalysis is what Eve has to do in order to \break the code". abstract examples Terminology cryptanalysis harder cryptography schemes Components plaintext is the message that Alice wants to send. ciphertext is the scrambled/unreadable thing she actually sends. encryption is the process of converting plaintext to ciphertext. decryption is the reverse process. Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes Components plaintext is the message that Alice wants to send. ciphertext is the scrambled/unreadable thing she actually sends. encryption is the process of converting plaintext to ciphertext. decryption is the reverse process. cryptanalysis is what Eve has to do in order to \break the code". Joe Fields Cryptography Usually a key must also be chosen (in advance) by Alice and Bob. If Eve knows the cryptosystem, she can attempt a \brute force" attack { try every possible key. abstract examples Terminology cryptanalysis harder cryptography schemes A cryptosystem The term cryptosystem is used to describe any systematic way to do encryption and decryption of messages. Joe Fields Cryptography If Eve knows the cryptosystem, she can attempt a \brute force" attack { try every possible key. abstract examples Terminology cryptanalysis harder cryptography schemes A cryptosystem The term cryptosystem is used to describe any systematic way to do encryption and decryption of messages. Usually a key must also be chosen (in advance) by Alice and Bob. Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes A cryptosystem The term cryptosystem is used to describe any systematic way to do encryption and decryption of messages. Usually a key must also be chosen (in advance) by Alice and Bob. If Eve knows the cryptosystem, she can attempt a \brute force" attack { try every possible key. Joe Fields Cryptography Arguably, this is why Japan and Germany lost World War II. Shannon's Maxim: \The enemy knows the system" (Claude Shannon (1916-2001) abstract examples Terminology cryptanalysis harder cryptography schemes security through obscurity People used to believe that a really Byzantine cryptosystem { for which Eve couldn't even guess what the possible keys could be { would allow Alice and Bob to communicate securely. Joe Fields Cryptography Shannon's Maxim: \The enemy knows the system" (Claude Shannon (1916-2001) abstract examples Terminology cryptanalysis harder cryptography schemes security through obscurity People used to believe that a really Byzantine cryptosystem { for which Eve couldn't even guess what the possible keys could be { would allow Alice and Bob to communicate securely. Arguably, this is why Japan and Germany lost World War II. Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes security through obscurity People used to believe that a really Byzantine cryptosystem { for which Eve couldn't even guess what the possible keys could be { would allow Alice and Bob to communicate securely. Arguably, this is why Japan and Germany lost World War II. Shannon's Maxim: \The enemy knows the system" (Claude Shannon (1916-2001) Joe Fields Cryptography abstract examples Terminology cryptanalysis harder cryptography schemes cribs If you have some idea what an encrypted message may be about, this allows you to make a list of \cribs." Cribs are words or phrases that may be part of the plaintext. Joe Fields Cryptography Tatoo a message on a slave's shaved head, then let their hair grow back. Yesterday, Oliver used a relatively easy secret message analyzer { really terrific! It has been claimed that the Al Qaeda network hides messages in the low bits of pixels in internet porn. abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes how can they decode it if they don't even know there is a message? Joe Fields Cryptography Yesterday, Oliver used a relatively easy secret message analyzer { really terrific! It has been claimed that the Al Qaeda network hides messages in the low bits of pixels in internet porn. abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes how can they decode it if they don't even know there is a message? Tatoo a message on a slave's shaved head, then let their hair grow back. Joe Fields Cryptography It has been claimed that the Al Qaeda network hides messages in the low bits of pixels in internet porn. abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes how can they decode it if they don't even know there is a message? Tatoo a message on a slave's shaved head, then let their hair grow back. Yesterday, Oliver used a relatively easy secret message analyzer { really terrific! Joe Fields Cryptography abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes how can they decode it if they don't even know there is a message? Tatoo a message on a slave's shaved head, then let their hair grow back. Yesterday, Oliver used a relatively easy secret message analyzer { really terrific! It has been claimed that the Al Qaeda network hides messages in the low bits of pixels in internet porn. Joe Fields Cryptography So, Attack at dawn on Friday would be encrypted as Dwwdfn dw gdzq rq iulgdb abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes Roman cryptography Supposedly, Julius Caesar invented a simple cryptosystem: shift each letter in a message 3 units up in the alphabet: Joe Fields Cryptography Dwwdfn dw gdzq rq iulgdb abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes Roman cryptography Supposedly, Julius Caesar invented a simple cryptosystem: shift each letter in a message 3 units up in the alphabet: So, Attack at dawn on Friday would be encrypted as Joe Fields Cryptography abstract examples steganography cryptanalysis the Caesar shift harder cryptography schemes Roman cryptography Supposedly, Julius Caesar invented a simple
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