Security and Encryption

What is Encryption

bullInformation is often stored and transmitted in a file

bull A plaintext file uses a common encoding format such as ASCII or Unicode to represent the characters of the file

bull Encryption is a translation of a file into a format that hides the content from selected parties a secret code ciphertext

Uses of Encryptionbull PrivacySecrecybullndash email messagesbullndash wireless phonesbull Securitybullndash passwordsbullndash wireless

networksbull Intellectual

Propertybullndash copy protection

bull Confidentialitybull ndash personnel recordsbull ndash medical recordsbull ndash transaction

recordsbull Authenticationbull ndash digital signaturesbull ndash login

What Is CryptographybullCryptography -- from the Greek for ldquosecret

writingrdquo -- is the mathematical ldquoscramblingrdquo of data so that only someone with the necessary key can ldquounscramblerdquo it

bullCryptography allows secure transmission of private information over insecure channels (for example packet-switched networks)

bullCryptography also allows secure storage of sensitive data on any computer

Technology and RiskbullTechnological advances created new risks

electronic communication makes information more easily available to more parties

long-term storage of sensitive data requires stronger encryption techniques

bull Some technologies actually reduce risk fiber optic cable strong encryption

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

What is Encryption

bullInformation is often stored and transmitted in a file

bull A plaintext file uses a common encoding format such as ASCII or Unicode to represent the characters of the file

bull Encryption is a translation of a file into a format that hides the content from selected parties a secret code ciphertext

Uses of Encryptionbull PrivacySecrecybullndash email messagesbullndash wireless phonesbull Securitybullndash passwordsbullndash wireless

networksbull Intellectual

Propertybullndash copy protection

bull Confidentialitybull ndash personnel recordsbull ndash medical recordsbull ndash transaction

recordsbull Authenticationbull ndash digital signaturesbull ndash login

What Is CryptographybullCryptography -- from the Greek for ldquosecret

writingrdquo -- is the mathematical ldquoscramblingrdquo of data so that only someone with the necessary key can ldquounscramblerdquo it

bullCryptography allows secure transmission of private information over insecure channels (for example packet-switched networks)

bullCryptography also allows secure storage of sensitive data on any computer

Technology and RiskbullTechnological advances created new risks

electronic communication makes information more easily available to more parties

long-term storage of sensitive data requires stronger encryption techniques

bull Some technologies actually reduce risk fiber optic cable strong encryption

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Uses of Encryptionbull PrivacySecrecybullndash email messagesbullndash wireless phonesbull Securitybullndash passwordsbullndash wireless

networksbull Intellectual

Propertybullndash copy protection

bull Confidentialitybull ndash personnel recordsbull ndash medical recordsbull ndash transaction

recordsbull Authenticationbull ndash digital signaturesbull ndash login

What Is CryptographybullCryptography -- from the Greek for ldquosecret

writingrdquo -- is the mathematical ldquoscramblingrdquo of data so that only someone with the necessary key can ldquounscramblerdquo it

bullCryptography allows secure transmission of private information over insecure channels (for example packet-switched networks)

bullCryptography also allows secure storage of sensitive data on any computer

Technology and RiskbullTechnological advances created new risks

electronic communication makes information more easily available to more parties

long-term storage of sensitive data requires stronger encryption techniques

bull Some technologies actually reduce risk fiber optic cable strong encryption

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

What Is CryptographybullCryptography -- from the Greek for ldquosecret

writingrdquo -- is the mathematical ldquoscramblingrdquo of data so that only someone with the necessary key can ldquounscramblerdquo it

bullCryptography allows secure transmission of private information over insecure channels (for example packet-switched networks)

bullCryptography also allows secure storage of sensitive data on any computer

Technology and RiskbullTechnological advances created new risks

electronic communication makes information more easily available to more parties

long-term storage of sensitive data requires stronger encryption techniques

bull Some technologies actually reduce risk fiber optic cable strong encryption

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Technology and RiskbullTechnological advances created new risks

electronic communication makes information more easily available to more parties

long-term storage of sensitive data requires stronger encryption techniques

bull Some technologies actually reduce risk fiber optic cable strong encryption

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

German Enigma Cipher MachinebullIn 1918 Arthur Scherbius filed for a patent for Enigma Cipher Machine and offered it to the German Navybull In 1926 German navy begins using Enigma Machine lightly modified from a commercial modelbullIn 1930 German armed forces introduced asignificantly modified military model

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Simple Cryptography

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Two basic principles

bullSubstitutionbullTHIS IS A SECRET (key n=3)bullWKLV LV D VHFUHWbullTranspositionbull THIS IS A SECRET (key 4213)bullIHSTSI S EAERTC

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Caesar Cipher

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Rotating Key Cipher

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Goals of CipherbullDiffussion

1048713 Small change in plaintext changes lots of ciphertext

1048713 Statistical properties of plaintext hidden in ciphertext

bull1048713 Confusion1048713 Statistical relationship between key and

ciphertext as complex as possible1048713 So need to design functions that produce

output that is diffuse and confused

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

General Principles

bullLonger keys make better ciphersbull1048713 Random keys make better ciphersbull1048713 Good ciphers produce ldquorandomrdquo

ciphertextbull1048713 Best keys are used once and thrown

away

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word

Public Key Cryptography

bullYour turnhellipWhat is itHow does it workInclude an analogyAny weaknessesIf you come across digital signatures what

are theyUse MS Word