**Binary**

Hexadecimal

Hexadecimal

**CyberPDX Cryptography**

Encoding

Encoding

**ASCII**

**Visual Encoders**

Before we get to encryption, we need to learn encoding

Representing information in ways computers recognize

101000001

321

Which one is 321?

Code 39 Code 128 UPC

All of them

ASCII maps 1-byte values to characters

Used in URLs, Web pages, e-mail

(in decimal)

100 10 1

How did we get these?

"Base-10"

Positions denote powers of 10

Digits 0-9 denote position values

101 million and one?

(Yes), but also 321 in binary (Base-2)

101000001

256 128 64 32 16 8 4 2 1

How did we

get these?

2 2 2 2 2 2 2 2 2

"Base-2"

Places denote powers of 2

Digits 0 and 1 denote place values

8 7 6 5 4 3 2 1 0

256 + 0 + 64 + 0 + 0 + 0 + 0 + 0 + 1 = 321

Binary group activity

With a partner

1) Find the decimal values of binary numbers below

x = 1 0 0 1 1

y = 0 1 0 0 1

x-y x+y

141

0x

141 in decimal?

(Yes), but also 321 in hexadecimal (Base-16)

000101000001

0x141

256 16 1

How did we

get these?

16 16 16

"Base-16"

2 1 0

1x256 + 4x16 + 1x1 = 321

0001 0100 0001

1 4 1

Places denote powers of 16

But, requires 16 distinct digit settings to denote values

Binary 0,1

Decimal 0,1,2,3,4,5,6,7,8,9

Hexadecimal 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

0x1AF

256 16 1

1x256 + 10x16 + 15x1 = 431

0x333231

3,355,185?

(Yes), but also "321" in ASCII

0x333231

0x33 0x32 0x31

'3' '2' '1'

Collaborate to decode the full message:

ASCII group activity

Snippet #1: 54 68 65 20 68 6F 6D 65 20 74 6F

Snippet #2: 65 76 65 72 79 6F 6E 65 20 69 73

Snippet #3: 74 6F 20 68 69 6D 20 68 69 73

Snippet #4: 63 61 73 74 6C 65 20 61 6E 64

Snippet #5: 66 6F 72 74 72 65 73 73 2E

Snippet #6: 45 64 77 61 72 64 20 43 6F 6B 65

**Steganography**

Is 321 here?

Maybe this will help

http://crypto.cyberpdx.org/static/psu_logo.jpg

http://exif.regex.info/

http://datalab.cs.pdx.edu/unplugged/baseconversion.html

Why hexadecimal?

Recall binary

Hexadecimal activity

Cryptography challenges

Read letter carefully

PDF files on the key drive are password protected with lowercase keys found by solving challenges

Flags in capital letters found by reading the PDF files (and some thinking) to be submitted to web site ( http://crypto.cyberpdx.org/ )

One set of challenges released each day

Solve by 8:30am the following day

Test your team's accounts

Help readily given by faculty in office hours at Ondine

Install Barcode and QR code scanning software

Each team member should go through challenge solutions

May be a time your team will need you!

10 10 10

2 1 0

Code 39

3x100 + 2x10 + 1x1

2) Decimal values of

http://datalab.cs.pdx.edu/unplugged/binarycards.html

= 19

= 9

16 8 4 2 1

x-y x+y

3) Binary representation of

10 = 01010

28 = 11100

Concealing messages or information within other nonsecret text or data

x-y = 10

x+y = 28

0x0CD

256 16 1

0x256 + 12x16 + 13x1

Hexadecimal example

0 + 192 + 13 = 205

Why should we care?

Computers use binary (bits) to store all information

Humans encode characters in pairs of hexadecimal digits

Each pair of hex digits is 8 bits or 1 byte

Bytes are the smallest unit of data for computers

Is this 321?

Encode bits as bar widths

Wide=1

Narrow=0

Plus spacing

Map patterns to character set

Code 39 misapplied

QR code (Quick Response)

2D barcode

Red squares for position and alignment

Red strips identify rows, columns of bits

Green denotes data type (text, URL, etc.)

Blue is version (number of modules)

Source: http://www.ucreative.com/articles/what-is-a-qr-code-and-how-does-it-work/

QR code (Quick Response)

Data encoded directly as bits in byte-sized modules

3

2

1

**Mini-race**

Set of encoding puzzles that ends with a riddle.

Meant for each of you to get practice and to teach each other

Give me the answer to the riddle to get wristbands for your team

256 128 64 32 16 8 4 2 1

Keep ASCII table around for later...