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Computer Security

Fundamentals

by Chuck Easttom

Chapter 8 Encryption

Chapter 8 Objectives

◼

◼

◼

◼

Explain the basics of encryption

Discuss modern cryptography methods

Select appropriate cryptography for your

organization

Understand the function and protocols of

VPNs

© 2019 Pearson, Inc.

Chapter 8 Encryption

2

Introduction

◼

Encryption

❑

❑

◼

Obfuscating the data so a key is required.

One critical part to the security puzzle.

Cryptography

❑

Requires mathematics

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

Cryptography Basics

◼

Decryption

❑

◼

Reversal of the scrambling protocol

Encryption

❑

Algorithm scrambles plain text

Sender and receiver agree on algorithm

❑

Message difficult to re-create without key

❑

© 2019 Pearson, Inc.

Chapter 8 Encryption

4

Cryptography Basics (cont.)

◼

Two basic types

◼

Single/symmetric key encryption

❑

❑

◼

Stream

Block

▪ Substitution and transposition

Public/asymmetric key encryption

© 2019 Pearson, Inc.

Chapter 8 Encryption

5

History of Encryption

◼

◼

Old as written communication and war

Caesar Cipher

❑

Shift cipher

◼

A DOG

❑

❑

❑

Shift 1 – B EPH

Shift 2 – C FQI

Shift negative 1 – Z CNF

© 2019 Pearson, Inc.

Chapter 8 Encryption

6

History of Encryption (cont.)

◼

Caesar Cipher

❑

❑

Frequency distribution cracks this simple

cipher.

Substitution alphabet.

◼

◼

Substitutes one letter in the alphabet for

another.

Caesar is a mono-alphabetic cipher.

© 2019 Pearson, Inc.

Chapter 8 Encryption

7

History of Encryption (cont.)

◼

ATBASH

Rail Fence

Vigenere

◼

Enigma

◼

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

8

History of Encryption (cont.)

◼

Multi-alphabetic

❑

Select multiple shifts

◼

◼

◼

❑

Shift 1, 2, –1

Rotate through the shifts

A DOG becomes B FNH

Old cipher considered weak today

© 2019 Pearson, Inc.

Chapter 8 Encryption

9

Binary Operations

◼

Binary Operations

❑

◼

AND, OR, XOR

Example of AND operation

1 1 0 1

1 0 0 1

1 0 0 1

© 2019 Pearson, Inc.

Chapter 8 Encryption

10

Binary Operations

◼

Example of OR operation

1 1 0 1

1 0 0 1

1 1 0 1

© 2019 Pearson, Inc.

Chapter 8 Encryption

11

Binary Operations

◼

Example of XOR operation

1 1 0 1

1 0 0 1

0 1 0 0

© 2019 Pearson, Inc.

Chapter 8 Encryption

12

Binary Operations

◼

XOR only reversible binary operation

❑

Convert plain text to ASCII

A DOG = 065 032 068 079 071

❑

Then, convert ASCII to binary

0100 0001, 0100 0100, 0100 1111, 0100 0111

© 2016 Pearson, Inc.

Chapter 8 Encryption

13

Binary Operations

◼

XOR the ASCII

0100 0001, 0100 0100, 0100 1111, 0100 0111

1111 0111, 1111 0111, 1111 0111, 1111 0111

1011 0110, 1011 0011, 1011 1000, 1011 0000

◼

Result is cipher text.

© 2019 Pearson, Inc.

Chapter 8 Encryption

14

Cryptography Terms

◼

◼

◼

◼

Key: The bits that are combined with the

plain text to encrypt it. In some cases this

is random numbers; in other cases it is the

result of some mathematical operation.

Plain text: The unencrypted text.

Cipher text: The encrypted text.

Algorithm: A mathematical process for

doing something.

© 2019 Pearson, Inc.

Chapter 8 Encryption

15

Modern Methods

◼

Single key (symmetric) encryption

❑

Same key to encrypt and decrypt

◼

Blowfish

❑

❑

❑

❑

Symmetric block cipher

Works on “blocks” of letters

Uses variable length key (32–448 bits)

Freeware

© 2019 Pearson, Inc.

Chapter 8 Encryption

16

Modern Methods (cont.)

◼

Data Encryption Standard (DES)

1.

Divided into 64-bit blocks; then transposed

2. Manipulated by 16 steps of encryption, using

56-bit key

3. Scrambled by a swapping algorithm

4. Transposed one final time

© 2019 Pearson, Inc.

Chapter 8 Encryption

17

Modern Methods (cont.)

◼

◼

Advanced Encryption Standard (AES).

Advanced Encryption Standard was the

algorithm eventually chosen to replace

DES. It is a block cipher that works on 128bit blocks. It can have one of three key

sizes of 128, 192, or 256 bits. This was

selected by the United States government

to be the replacement for DES and is now

the most widely used symmetric key

algorithm.

© 2019 Pearson, Inc.

Chapter 8 Encryption

18

Modern Methods (cont.)

◼

One major problem with symmetric key

encryption

How do you transmit the symmetric key?

◼

The answer: public key encryption

© 2019 Pearson, Inc.

Chapter 8 Encryption

19

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

❑

❑

One key (public key) used to encrypt .

One key (private key) used to decrypt.

Only holder of a private key can decrypt

messages.

© 2019 Pearson, Inc.

Chapter 8 Encryption

20

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

❑

❑

Depends on large prime numbers, factoring,

and number theory.

Public key encryption is most widely used.

Pretty Good Privacy (PGP):

◼

◼

Freeware

Quite secure

© 2019 Pearson, Inc.

Chapter 8 Encryption

21

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

Pretty Good Privacy (PGP)

◼

◼

◼

Freeware

Phil Zimmerman – 2004

Quite secure

© 2019 Pearson, Inc.

Chapter 8 Encryption

22

Modern Methods (cont.)

The MIT Distribution Center for PGP home page

(http://web.mit.edu/network/pgp.html)

© 2019 Pearson, Inc.

Chapter 8 Encryption

23

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

RSA

◼

◼

◼

◼

You start by generating two large random primes, p

and q, of approximately equal size. Now you need

to pick two numbers so that when multiplied

together the product will be the size you want (that

is, 1024 bits, 2048 bits, and so on).

Now multiply p and q to get n.

Let n = pq

Let m = (p – 1)(q – 1)

© 2019 Pearson, Inc.

Chapter 8 Encryption

24

Modern Methods (cont.)

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

25

Modern Methods (cont.)

The RSA Security home page

(http://www.rsasecurity.com)

© 2019 Pearson, Inc.

Chapter 8 Encryption

26

Modern Methods (cont.)

◼

Legitimate versus fraudulent encryption

❑

Warning signs of frauds

◼

◼

◼

Unbreakable

Certified

Inexperienced people

© 2019 Pearson, Inc.

Chapter 8 Encryption

27

Avoid ‘bad’ crypto

◼

◼

◼

◼

Unbreakable

Unhackable

Secret algorithm

Kerhoff’s principle

© 2019 Pearson, Inc.

Chapter 8 Encryption

28

Digital Signatures

◼

A digital signature is not used to ensure the confidentiality of a

message, but rather to guarantee who sent the message. This is

referred to as nonrepudiation. Essentially, it proves who the sender

is. Digital signatures are actually rather simple, but clever. They

simply reverse the asymmetric encryption process. Recall that in

asymmetric encryption the public key (which anyone can have

access to) is used to encrypt a message to the recipient, and the

private key (which is kept secure and private) can decrypt it. With a

digital signature, the sender encrypts something with his private key.

If the recipient can decrypt that with the sender’s public key, then it

must have been sent by the person purported to have sent the

message.

© 2019 Pearson, Inc.

Chapter 8 Encryption

29

Hash

◼

Hashing is a type of cryptographic algorithm

that has some specific characteristics. First

and foremost it is one way. That means you

cannot “unhash” something. The second

characteristic is that you get a fixed-length

output no matter what input is given. Finally,

it should have few or no collisions. A collision

is when two different inputs provide the same

output.

© 2019 Pearson, Inc.

Chapter 8 Encryption

30

Hash – cont.

◼

◼

◼

◼

MD5

SHA1

SHA2

SHA3

© 2019 Pearson, Inc.

Chapter 8 Encryption

31

3

2

VERY Simple Illustration of

Rainbow Tables

Password

MD5 Hash (in Hex)

Password

MD5 Hash (in Hex)

aaaa

74b87337454200d4d33

f80c4663dc5e5

aaaaa

594f803b380a41396ed

63dca39503542

aaab

4c189b020ceb022e0ec

c42482802e2b8

aaabb

120858a7016efcfab669

67b834e9153c

aaac

3963a2ba65ac8eb1c6e

2140460031925

aaacc

ee43671d755ac457cfe

6e32d1894788e

aaa1

39dc4f1ee693e5adabd

dd872247e451f

aaa1a

5bbac29650eb36b4de1

6885c190a9fa3

aaa2

0ad346c93c16e85e2cb

117ff1fcfada3

aaa2a

597f0ce6d11567cc691b

3f5df35594cb

aaa4

ee93fca7c150d9c548af

f721c87d0986

aaa4a

4305dc076b3ba2bf8d5

5524cddf5a72d

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

3

Hash – Salt

Random bits added to further secure encryption or hashing. Most often encountered with hashing, to

prevent Rainbow Table attacks.

◼

Essentially the salt is intermixed with the message that is to be

hashed. Consider this example. You have a password that is

pass001

in binary that is

01110000 01100001 01110011 01110011 00110000 00110000

00110001

A salt algorithm would insert bits periodically, lets assume for our

example that we insert bits every 4th bit giving us

0111100001 0110100011 0111100111 0111100111 0011100001

0011100001 0011100011

If you convert that to text you would get

xZ7�� #

◼

◼

◼

◼

◼

◼

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

Historical Steganography

◼

◼

◼

The ancient Chinese wrapped notes in wax

and swallowed them for transport.

In ancient Greece a messenger’s head might

be shaved, a message written on his head,

then his hair was allowed to grow back.

In 1518 Johannes Trithmeus wrote a book on

cryptography and described a technique

where a message was hidden by having each

letter taken as a word from a specific column.

© 2019 Pearson, Inc.

Chapter 8 Encryption

Historical Steganography Continued

◼

◼

During WW II the French Resistance sent

messages written on the backs of couriers

using invisible ink

Microdots are images/undeveloped film the

size of a typewriter period, embedded on an

innocuous documents. These were said to be

used by spy’s during the Cold War.

© 2019 Pearson, Inc.

Chapter 8 Encryption

Steganography Terms

◼

◼

◼

Payload is the data to be covertly

communicated.

The carrier is the signal, stream, or data file

into which the payload is hidden. This is also

sometimes called the cover object.

The channel is the type of medium used.

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

7

Cryptanalysis

◼

◼

◼

◼

Ciphertext Only Attack

Known plain text

Chosen plain text

Related Key

© 2019 Pearson, Inc.

Chapter 8 Encryption

Summary

◼

◼

Encryption is a basic element of security.

Encrypting data when transmitting is an

integral part of any security plan.

© 2019 Pearson, Inc.

Chapter 8 Encryption

38

…

Purchase answer to see full

attachment

Fundamentals

by Chuck Easttom

Chapter 8 Encryption

Chapter 8 Objectives

◼

◼

◼

◼

Explain the basics of encryption

Discuss modern cryptography methods

Select appropriate cryptography for your

organization

Understand the function and protocols of

VPNs

© 2019 Pearson, Inc.

Chapter 8 Encryption

2

Introduction

◼

Encryption

❑

❑

◼

Obfuscating the data so a key is required.

One critical part to the security puzzle.

Cryptography

❑

Requires mathematics

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

Cryptography Basics

◼

Decryption

❑

◼

Reversal of the scrambling protocol

Encryption

❑

Algorithm scrambles plain text

Sender and receiver agree on algorithm

❑

Message difficult to re-create without key

❑

© 2019 Pearson, Inc.

Chapter 8 Encryption

4

Cryptography Basics (cont.)

◼

Two basic types

◼

Single/symmetric key encryption

❑

❑

◼

Stream

Block

▪ Substitution and transposition

Public/asymmetric key encryption

© 2019 Pearson, Inc.

Chapter 8 Encryption

5

History of Encryption

◼

◼

Old as written communication and war

Caesar Cipher

❑

Shift cipher

◼

A DOG

❑

❑

❑

Shift 1 – B EPH

Shift 2 – C FQI

Shift negative 1 – Z CNF

© 2019 Pearson, Inc.

Chapter 8 Encryption

6

History of Encryption (cont.)

◼

Caesar Cipher

❑

❑

Frequency distribution cracks this simple

cipher.

Substitution alphabet.

◼

◼

Substitutes one letter in the alphabet for

another.

Caesar is a mono-alphabetic cipher.

© 2019 Pearson, Inc.

Chapter 8 Encryption

7

History of Encryption (cont.)

◼

ATBASH

Rail Fence

Vigenere

◼

Enigma

◼

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

8

History of Encryption (cont.)

◼

Multi-alphabetic

❑

Select multiple shifts

◼

◼

◼

❑

Shift 1, 2, –1

Rotate through the shifts

A DOG becomes B FNH

Old cipher considered weak today

© 2019 Pearson, Inc.

Chapter 8 Encryption

9

Binary Operations

◼

Binary Operations

❑

◼

AND, OR, XOR

Example of AND operation

1 1 0 1

1 0 0 1

1 0 0 1

© 2019 Pearson, Inc.

Chapter 8 Encryption

10

Binary Operations

◼

Example of OR operation

1 1 0 1

1 0 0 1

1 1 0 1

© 2019 Pearson, Inc.

Chapter 8 Encryption

11

Binary Operations

◼

Example of XOR operation

1 1 0 1

1 0 0 1

0 1 0 0

© 2019 Pearson, Inc.

Chapter 8 Encryption

12

Binary Operations

◼

XOR only reversible binary operation

❑

Convert plain text to ASCII

A DOG = 065 032 068 079 071

❑

Then, convert ASCII to binary

0100 0001, 0100 0100, 0100 1111, 0100 0111

© 2016 Pearson, Inc.

Chapter 8 Encryption

13

Binary Operations

◼

XOR the ASCII

0100 0001, 0100 0100, 0100 1111, 0100 0111

1111 0111, 1111 0111, 1111 0111, 1111 0111

1011 0110, 1011 0011, 1011 1000, 1011 0000

◼

Result is cipher text.

© 2019 Pearson, Inc.

Chapter 8 Encryption

14

Cryptography Terms

◼

◼

◼

◼

Key: The bits that are combined with the

plain text to encrypt it. In some cases this

is random numbers; in other cases it is the

result of some mathematical operation.

Plain text: The unencrypted text.

Cipher text: The encrypted text.

Algorithm: A mathematical process for

doing something.

© 2019 Pearson, Inc.

Chapter 8 Encryption

15

Modern Methods

◼

Single key (symmetric) encryption

❑

Same key to encrypt and decrypt

◼

Blowfish

❑

❑

❑

❑

Symmetric block cipher

Works on “blocks” of letters

Uses variable length key (32–448 bits)

Freeware

© 2019 Pearson, Inc.

Chapter 8 Encryption

16

Modern Methods (cont.)

◼

Data Encryption Standard (DES)

1.

Divided into 64-bit blocks; then transposed

2. Manipulated by 16 steps of encryption, using

56-bit key

3. Scrambled by a swapping algorithm

4. Transposed one final time

© 2019 Pearson, Inc.

Chapter 8 Encryption

17

Modern Methods (cont.)

◼

◼

Advanced Encryption Standard (AES).

Advanced Encryption Standard was the

algorithm eventually chosen to replace

DES. It is a block cipher that works on 128bit blocks. It can have one of three key

sizes of 128, 192, or 256 bits. This was

selected by the United States government

to be the replacement for DES and is now

the most widely used symmetric key

algorithm.

© 2019 Pearson, Inc.

Chapter 8 Encryption

18

Modern Methods (cont.)

◼

One major problem with symmetric key

encryption

How do you transmit the symmetric key?

◼

The answer: public key encryption

© 2019 Pearson, Inc.

Chapter 8 Encryption

19

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

❑

❑

One key (public key) used to encrypt .

One key (private key) used to decrypt.

Only holder of a private key can decrypt

messages.

© 2019 Pearson, Inc.

Chapter 8 Encryption

20

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

❑

❑

Depends on large prime numbers, factoring,

and number theory.

Public key encryption is most widely used.

Pretty Good Privacy (PGP):

◼

◼

Freeware

Quite secure

© 2019 Pearson, Inc.

Chapter 8 Encryption

21

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

Pretty Good Privacy (PGP)

◼

◼

◼

Freeware

Phil Zimmerman – 2004

Quite secure

© 2019 Pearson, Inc.

Chapter 8 Encryption

22

Modern Methods (cont.)

The MIT Distribution Center for PGP home page

(http://web.mit.edu/network/pgp.html)

© 2019 Pearson, Inc.

Chapter 8 Encryption

23

Modern Methods (cont.)

◼

Public key (asymmetric) encryption

❑

RSA

◼

◼

◼

◼

You start by generating two large random primes, p

and q, of approximately equal size. Now you need

to pick two numbers so that when multiplied

together the product will be the size you want (that

is, 1024 bits, 2048 bits, and so on).

Now multiply p and q to get n.

Let n = pq

Let m = (p – 1)(q – 1)

© 2019 Pearson, Inc.

Chapter 8 Encryption

24

Modern Methods (cont.)

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

25

Modern Methods (cont.)

The RSA Security home page

(http://www.rsasecurity.com)

© 2019 Pearson, Inc.

Chapter 8 Encryption

26

Modern Methods (cont.)

◼

Legitimate versus fraudulent encryption

❑

Warning signs of frauds

◼

◼

◼

Unbreakable

Certified

Inexperienced people

© 2019 Pearson, Inc.

Chapter 8 Encryption

27

Avoid ‘bad’ crypto

◼

◼

◼

◼

Unbreakable

Unhackable

Secret algorithm

Kerhoff’s principle

© 2019 Pearson, Inc.

Chapter 8 Encryption

28

Digital Signatures

◼

A digital signature is not used to ensure the confidentiality of a

message, but rather to guarantee who sent the message. This is

referred to as nonrepudiation. Essentially, it proves who the sender

is. Digital signatures are actually rather simple, but clever. They

simply reverse the asymmetric encryption process. Recall that in

asymmetric encryption the public key (which anyone can have

access to) is used to encrypt a message to the recipient, and the

private key (which is kept secure and private) can decrypt it. With a

digital signature, the sender encrypts something with his private key.

If the recipient can decrypt that with the sender’s public key, then it

must have been sent by the person purported to have sent the

message.

© 2019 Pearson, Inc.

Chapter 8 Encryption

29

Hash

◼

Hashing is a type of cryptographic algorithm

that has some specific characteristics. First

and foremost it is one way. That means you

cannot “unhash” something. The second

characteristic is that you get a fixed-length

output no matter what input is given. Finally,

it should have few or no collisions. A collision

is when two different inputs provide the same

output.

© 2019 Pearson, Inc.

Chapter 8 Encryption

30

Hash – cont.

◼

◼

◼

◼

MD5

SHA1

SHA2

SHA3

© 2019 Pearson, Inc.

Chapter 8 Encryption

31

3

2

VERY Simple Illustration of

Rainbow Tables

Password

MD5 Hash (in Hex)

Password

MD5 Hash (in Hex)

aaaa

74b87337454200d4d33

f80c4663dc5e5

aaaaa

594f803b380a41396ed

63dca39503542

aaab

4c189b020ceb022e0ec

c42482802e2b8

aaabb

120858a7016efcfab669

67b834e9153c

aaac

3963a2ba65ac8eb1c6e

2140460031925

aaacc

ee43671d755ac457cfe

6e32d1894788e

aaa1

39dc4f1ee693e5adabd

dd872247e451f

aaa1a

5bbac29650eb36b4de1

6885c190a9fa3

aaa2

0ad346c93c16e85e2cb

117ff1fcfada3

aaa2a

597f0ce6d11567cc691b

3f5df35594cb

aaa4

ee93fca7c150d9c548af

f721c87d0986

aaa4a

4305dc076b3ba2bf8d5

5524cddf5a72d

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

3

Hash – Salt

Random bits added to further secure encryption or hashing. Most often encountered with hashing, to

prevent Rainbow Table attacks.

◼

Essentially the salt is intermixed with the message that is to be

hashed. Consider this example. You have a password that is

pass001

in binary that is

01110000 01100001 01110011 01110011 00110000 00110000

00110001

A salt algorithm would insert bits periodically, lets assume for our

example that we insert bits every 4th bit giving us

0111100001 0110100011 0111100111 0111100111 0011100001

0011100001 0011100011

If you convert that to text you would get

xZ7�� #

◼

◼

◼

◼

◼

◼

◼

© 2019 Pearson, Inc.

Chapter 8 Encryption

Historical Steganography

◼

◼

◼

The ancient Chinese wrapped notes in wax

and swallowed them for transport.

In ancient Greece a messenger’s head might

be shaved, a message written on his head,

then his hair was allowed to grow back.

In 1518 Johannes Trithmeus wrote a book on

cryptography and described a technique

where a message was hidden by having each

letter taken as a word from a specific column.

© 2019 Pearson, Inc.

Chapter 8 Encryption

Historical Steganography Continued

◼

◼

During WW II the French Resistance sent

messages written on the backs of couriers

using invisible ink

Microdots are images/undeveloped film the

size of a typewriter period, embedded on an

innocuous documents. These were said to be

used by spy’s during the Cold War.

© 2019 Pearson, Inc.

Chapter 8 Encryption

Steganography Terms

◼

◼

◼

Payload is the data to be covertly

communicated.

The carrier is the signal, stream, or data file

into which the payload is hidden. This is also

sometimes called the cover object.

The channel is the type of medium used.

© 2019 Pearson, Inc.

Chapter 8 Encryption

3

7

Cryptanalysis

◼

◼

◼

◼

Ciphertext Only Attack

Known plain text

Chosen plain text

Related Key

© 2019 Pearson, Inc.

Chapter 8 Encryption

Summary

◼

◼

Encryption is a basic element of security.

Encrypting data when transmitting is an

integral part of any security plan.

© 2019 Pearson, Inc.

Chapter 8 Encryption

38

…

Purchase answer to see full

attachment

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