Fmdszqujpo!
Encryption!
Encryption
 Group Activity 1:
 Take the message you were given, and
create your own encryption.
 You can encrypt it anyway you want
 Try to make an interesting version that
you think no other group will be able to
guess!
Encryption
 What do you all think Encryption is?
 Where do you think a good place is to
use encryption?
Encryption
 To change information from one form
to another especially to hide its
meaning. (from the merriam-webster
dictionary)
 In cryptography, encryption is the
process of encoding messages or
information in such a way that only
authorized parties can read it. (from our
favorite site Wikipedia)
Encoding
 Encoding is the act of transforming
data so that it may be properly
consumed by another party
 Encoding is not used for security
purposes
 Common Encoding Schemes
 HTML
 URL
 Unicode
 Hex
Encryption

Encryption is similar to encoding,
except it implements the use of a key

A key is typically a random string of
bits used to scramble and unscramble
data

Different types of Encryption



Symmetric Key Encryption
Public Key Encryption
Common Encryption Schemes



WEP
TKIP
AES-CCMP
Encryption
Exhaustive Key Search
Cracking Activity 1
 For this activity, we will list each of the messages up here, and then
each group should choose a message and try to crack the encryption
and get the message.
Cracking Activity 1
 The messages are:
More Definitions, yay
 There are 2 types of encryption, weak encryption and strong encryption.
 Weak encryption means that although it is encrypted, it is a simple
algorithm, or simple way to encrypt it, and can be cracked in minutes to
anything less than a day or so. An example of this is from a security flaw
found in March. This flaw is from the days when the government enforced
that products be exported with weak encryption, but then was forgotten, and
wasn’t discovered till this year, leaving a lot of time for any number of
people to exploit it. The encryption was 512 bits, which can be cracked in
about 7 hours if you have a good enough set of computers (or using a cloud
of computers).
Definitions cont.
 Strong encryption means that the data/message is encrypted with
either a very complex algorithm, or it is encrypted enough times that
it takes a long time to decrypt. An example is that you use 2048 bit
encryption, or if you want to keep the weak encryption algorithm,
you can encrypt the data multiple times to make it stronger (like
encrypting a message with one method, then encrypting the result
with another, and so on for 5 different encrypted algorithms).
Definitions cont.
 One last definition that is good to know is what we mean when we
say we will crack encryption. When we say crack we mean break it or
decrypt it in some shape or form.
Example 1 – Caesar cipher
Example 1 – Caesar cipher
 A Caesar cipher is an algorithm that
uses the English alphabet to change a
message into something else. You
choose a number from 1 to 25, and for
each letter in the message you want to
encrypt, you add the number to it and
change to the new letter.
Example 1 – Caesar cipher
 Let’s say we want to take this phrase ‘thisisencryptionclass’ and use the Caesar
cipher to encrypt it. Let’s say we choose 5 as our ‘key’, which means the value we
want to change it with. First thing we can do is right out the alphabet from 0 to
25, and place the letters with the numbers.
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
 abcdef ghi j k
l m n o p q
r s
t
u v w x y z
Example 1 – Caesar cipher
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
 abcdef ghi j k
l m n o p q
r s
t
 this
is
encryption
 19 7 8 18
8 18
4 13 2 17 24 15 19 8 14 13
u v w x y z
class
2 11 0 18 18
 So the message in number form is:
 19 7 8 18 8 18 4 13 2 17 24 15 19 8 14 13 2 11 0 18 18
Example 1 – Caesar cipher
 Ok, now that we have the message as a number, let’s convert it using the key.
 Our key = 5 in this case, so add 5 to every number (and when it hits 25, start back
at 0 ie. 23 + 5 = 25 + 3 = 2
 19 7 8 18 8 18 4 13 2 17 24 15 19 8 14 13 2 11 0 18 18
 +5 +5 …..
…. +5 +5
 24 12 13 23 13 23 9 18 7 22 3 20 24 13 19 18 7 16 5 23 23
Example 1 – Caesar cipher
 Finally, let’s convert that back to letters:
 (remember:
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
 abcdef ghi j k
l m n o p q
r s
t
u v w x y z
 24 12 13 23 13 23 9 18 7 22 3 20 24 13 19 18 7 16 5 23 23
 y
mn x
n x j s hw du y n t
s h q f x x
Example 1 – Caesar cipher
 That means our original message: thisisencryptionclass
 Is now encrypted and looks like this:
 ymnxnxjshwduyntshqfxx
 Pretty simple right?
Example 2 – Substitution Cipher
Example 2 – Substitution Cipher
 The Substitution cipher goes one step further, and instead of using a single key,
we just arbitrarily change the way we have the letters.
 For this example, let’s use the following for our substitution key:
 a b c d e f g h i j k l m n o p q r s t u v w x y z
 j d k e b o a p r il u m n wq s f z x c v b s t y
Example 2 – Substitution Cipher
 a b c d e f g h i j k l m n o p q r s t u v w x y z
 j d k e b o a p r il u m n wq s f z x c v b s t y
 Now, using the same message we had in example one, we substitute each letter for
the one in the key we made.
 thisisencryptionclass is the message and gets encrypted to:
 thisisencryptionclass
 xprzrzbnkf tqxrwnkujzz
Example 3
Example 3
 For this example, we will explore public/private key encryption
 First off, go to https://www.igolder.com/PGP/
 We will use this site for the public/private key encryption
Example 3
 unencrypted message:
 thisisencryptionclass
Example 3

public key:

-----BEGIN PGP PUBLIC KEY BLOCK-----

Version: BCPG C# v1.6.1.0

mQENBFWUN4IBCACLRN0U0mcGe69UWvc0k7ZYZ5NH1eyIqpRzuISgjvC3AUBWqROk

yveE/zKUDBcYTge3G2yEOuAfTA6lCGPhXfSug6un9r1ddWcmfQK4BSVqFurlZpcC

x10f5ZLsIsJyDXML8GgKk3q0HhPxiE9qVnrhq1lV1KHaAaf60ifbr2dpTZkxLP9Q

hd/1it+wpByNO6xq+lx47CVbOoiCDIQxqPI1CixqnZGmFQ8MNf5dqtDN2i6aVoIb

TtYQSQppKO/bUG6//8mosmWfCQ9T7dHDRgX6KRVTv6PxsmXXFuj4iurcjFPK+9GP

mBf/ml8LwxhHM0b2wc2RTouc7KMrZ2yEQ2VHABEBAAG0HHdiZjAwMDdAdGlnZXJt
Example 3

YWlsLmF1YnVybi5lZHWJARwEEAECAAYFAlWUN4IACgkQnqgOCvo1SJWYiAf/S8bH

P/nUwfVTwyPQ4SHmhA7Dk4ywYuAsrMp6zuaHlPu1s21CMc88GLupcaT8CNdb9I7J

qZeTKVUwRlZAR/CkkF8IcAq/02QrNrZA9Uj0ZaGvxvy9x6MjTazDPkqPJ7IoYmIG

BlvSwGY2LQW5piuHuBgi2VSv8g3d1/4unVph0iiqCosAKldHrLJBkKe0evr0eF1H

BG1htjf9M5t2GyUk2OQ/rw+wYE2bYPZQjtYdgjE3U+hyZpBotrTQFl4ZvuDQdffU

ok2Hrw/vAy92KlM1UcjBO7m2VV52e5TdUVru/tnhvKADzpAn3LgQUVbj5W0GXPds

T+qMeOSA6Iw2fO8gsg==

=LzLX

-----END PGP PUBLIC KEY BLOCK-----
Example 3

encrypted message:

-----BEGIN PGP MESSAGE-----

Version: BCPG C# v1.6.1.0

hQEMA56oDgr6NUiVAQf+OZxioO1wGz3nnEImnyjrKViYBCN4boM+gKGiVo2RRPWw

+Pw8FDyjL2jO8CiX1+UTTZma0x9IXxHhoiQbA5Yncy9Hkn98SuPjvAm4CBvVqwTt

p4l6vm8eGdN8PqHfyGOVgbmvyoAfF8ciG5v5WLk3hJOUYy5t8MHSEltK/DA2RWQw

muUt5ExVxV7usHjUknRXT8FMbRfBZ+maGR5AxLbYnxFwQG5gkldjT4FbXI/cSxEC

p1dgUBL9+TLB/S2SCUCTiblpAn6AlaSfA3lpSU767aoRFhFqdiX+ObYDM6duOXNG

/VB80WwC3T9hMeHy1+KMPKeX3rfWRFmYmC8OfhCroskzr7AEPSOX19hwGijRPpUi

8IcaQyMcZ+mvuyIXP2XAtZgwDjWU9/twrQII1oUI/py6Tsq5

=5kkc

-----END PGP MESSAGE-----
Cracking Activity 2
 Let’s go to this website to do some encryption and decryption:
https://picoctf.com/crypto_mats/index.html
 As a group, create a few messages
 Then take those messages and encrypt them
 Next, bring them up to me and put a note that tells me which encryption you used
for it
 Finally, each group should choose a few (not your own) and try to decrypt them.
Once you’ve decrypted them, tell us which you chose, what encryption it was, and
what the message is
Public/Private Key Activity
 Go to the website: https://www.igolder.com/PGP/
 Split each group in half, and each half will play a role
 One will be the owner of the public/private keys, and the other will be the one to
send the message
 The owner should give the sender their public key, and the sender should use the
public key to encrypt the message. The sender then gives the message to the
owner, who decrypts it using the private key and password for their keys
 Next, each half should reverse roles
 Finally, both halves will be owners and senders.