Book Review ,Weekly Summary and Lab work
Shrikaa
AdvancedPersistentThreatHacking-week7.pptxAdvanced Persistent Threat Hacking Week 7
By
Professor Henry A. McKelvey
Remote Presence Reconnaissance (Finding out about people)
Information
Home Addresses
Travel Habits
Places Frequented
Associations (Business and Personal)
Information on People
Where to look
Spokeo
Intelius
People Finder
Many public and private databased
Place People Go (Easier Said Than Done)
Happy Hour
Team Functions
After Hours get away
Social Spear Phishing
Uses secondary targets as entry vectors
Family members
Friends
Associates
Target goal
Compromise computers of
Friends (Why)
Family (Why)
Client Hacking
After all else has failed, go in through the front door
Hack the Client instead of the network
Possible targets
Smart Phones
Tablets
E-readers
Point of Sale Systems
Specialized handheld systems
Now Let’s talk about Base64
What is Encoding?
What is Encryption?
What is Base64?
How is Base64 Used?
How does the Algorithm Work?
Why is Base64 so weak?
What are some issues to know about Base64
What is Encoding?
Encoding is the process of transforming information from one format into another.
– Transfer
– Storage
– Formatting (An example would be changing text to binary)
What is Encryption?
a type of encoding that obscures information to make it unreadable without a specific key.
An example would be the Caesar Cypher. Without knowledge of the cypher “key” of Knowledge about the cypher decryption is hard.
What is Base64?
Positional notation – a quadrosexagesimal number system.
What is a quadrosexagesimal number?
A number that is broken up into four sets of six
Numerals 0-9, alphabetical characters a-z and A-Z plus two special characters (all printable ASCII)
VGhlIHF1aWNrIGJyb3duIGZveCByYW4gb3ZlciB0aGUgbGF6eSBkb2c=
0-9 are used
a-z and A-Z are used
\ = are used (= is used for pad) (pad means padding or filling)
Base64 Symbol Layout
What is Base64 Used For?
“Binary to text” encoding.
Primarily used in SMTP – simple mail transfer protocol allows only 7-bit ASCII characters to be used.
Base64 will encode any bit stream as a sequence of 7-bit ASCII characters (ie. Binary data to plaintext).
Multipurpose Internet Mail Extensions
UTF-7
Anti-spam evasion
Binary data embedded in XML
How does the Algorithm Work?
Binary data is split into groups of 24 bits (3 bytes), then
split into 6-bit chunks and converted to the corresponding
ASCII characters.
See next page
How does the Algorithm Work? (Cont)
Part of the original bit stream = 011010110110101001101011
24 bits = 3 bytes
6-bit chunks = 011010 110110 101001 101011
4 sets of 6
Decimal Conversion = 26 54 41 43
The binary 011010 is decimal 26
The binary 110110 is decimal 54
The binary 101001 is decimal 41
The binary 101011 is decimal 43
Base 64 Conversion = a2pr
The Decimal 26 is ASCII a
The Decimal 54 is ASCII 2
The Decimal 41 is ASCII p
The Decimal 43 i s ASCII r
Odd Number of Bits
What if we don't have a multiple of 3 bytes in our bit stream? (We have to get a little creative).
01100010011011000111010101100101
Becomes
011000 100110 110001 110101
24 38 49 53
Ymx1
011001 01xxxx xxxxxx xxxxxx
25 26
ZQ
which translates to
011000 100110 110001 110101
24 38 49 53
Ymx1
011001 010000 000000 000000
25 26 0 0
ZQ==
Why is Base64 weak
If you think about it Base64 is simple (refer to the chart), which allows it to have flaws, but still be useful in some case such as its use in SMTP to provide a basic level of encryption which is a form of encoding
Base64 is predictable and too well known as a standard.
Decryption can be done with simple tools such as with a pencil and paper. Also a a little time.
Some of the issues with Base 64
33% increase in size of the file being encoded
ASCII85, Quoted-printable, 8BITMIME
Privacy-Enhanced Electronic Mail was the first place where base64 was used
Headers usually describe if a message is encoded in base64, it is up to the client to translate (client side translation)
