This document discusses the Blowfish encryption algorithm and the Nmap network scanning tool. It begins with an outline of the topics to be covered, which include an introduction to Blowfish, its structure and cryptanalysis, a paper on modifying Blowfish using multiple keys, and an overview of Nmap including its features and usage for port scanning networks. The document provides technical details and code examples for how Blowfish encryption works, discusses its security and comparisons to other algorithms, and outlines how Nmap can be used to detect operating systems, services, and vulnerabilities on targeted systems.

1. FACULITY OF ELECTRONIC
TECNOLOGY
COMPUTETR ENGINEERING
(MSc)
By: Haitham Farag Daw
1
Cryptography andCryptography and
Network SecurityNetwork Security

2. OutLine
2
Blowfish Encryption Algorithm
Paper Search
Nmap Tool

3. Blowfish Encryption
Algorithm
3
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4. Main point
 Introduction
 Structure
 Cryptanalysis
 Comparison
 References
4

5. Introduction
 designed in 1993 by Bruce Blowfish
 64-bit block cipher with variable length key
 Large key-dependent S-boxes
 More resistant to cryptanalysis
 Key-dependent permutations
 Diverse Mathematical Operations
 Combine XOR and addition
5

6. Continue
 Fast
 Compact It can run in less than 5K of memory.
 Simple to code
 Easily modifiable for different security levels
 Secure: The key length is variable ,it can be in
the range of 32~448 bits: default 128 bits key
length.
 Unpatented and royality-free.
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7. Structure of BF
 Feistel iterated block cipher
 Scalable Key (32 to 448 bits)
 Simple operation that are efficient on
microprocessors
 XOR, Addition, Table lookup, etc
 Employ Precomputable Subkeys
 Variable number of iterations
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8. 8

9. Implementation: Encryption
( )
171617
181617
11
111
PRR
PLL
PLR
RPLFL
iii
iiii
⊕=
⊕=
⊕=
⊕⊕=
−−
−−−
Wikipedia,
http://en.wikipedia.org/wiki/Image:BlowfishDiagram.png
Arrays:
P – Number of rounds + 2 elements
4 S-boxes – 256 elements
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10. Implementation: Function F(x(
( ) [ ] [ ]( ) [ ]( )
[ ]07
81516232431031
4
321
−
−−−−
+
⊕+=
XS
XSXSXSXF
Wikipedia,
http://upload.wikimedia.org/wikipedia/en
/8/81/BlowfishFFunction.png
Addition is mod 232
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11. Data Encryption
• Divide 64-bits into two 32-bit halves: XL, XR
• For i = 1 to 16
o XL = XL XOR Pi
o XR=F(XL) XOR XR
o Swap XL and XR
• Swap XL and XR (Undo the last swap )
• XR=XR XOR P17
• XL = XL XOR P18
• Concatenate XL and XR
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12. Cryptanalysis
 Differential Attack
 After 4 rounds a differential attack is no better than a brute
force attack
 Weak Keys
 S-box collisions
 blowfish algorithm has yet to be cracked as the key size
is high, requires 2448
combinations
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13. Future Concerns
 Simplifications
 Fewer and Smaller S-boxes
 Fewer Iterations
 On-the-fly subkey calculation
 Twofish
 AES Finalist
 128-bit Block Size
 More Operations
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14. Comparison
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15. References
 Wikipedia (for illustrations)
 http://en.wikipedia.org/wiki/Blowfish_cipher
 Applied Cryptography
 Bruce Schneier
 John Wiley and Sons, Inc. 1996
 The Blowfish Paper
 http://www.schneier.com/paper-blowfish-fse.html
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16. Paper Search
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16

17. New Approach for Modifying Blowfish
Algorithm by Using
Multiple Keys
by
Afaf et al in
VOL.11 No.3, March 2011, Amman, Jordan,
Baghdad, Iraq
17

18. Nmap Tool
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19. Outline
Introduction
Port Scanning
 Nmap
 Anti-Port Scanning
 Reference
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20. Introduction
IP Addresses: Finding out an IP Address
 Through Instant Messaging Software
 Through Internet Relay Chat
 Through Your website
 Through Email Headers
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21. 21
Port Scanning
 Port Scanning is normally the first step that an
attacker undertakes.
 List of Open Ports
 Services Running
 Exact Names and Versions of all the Services or
Daemons.
 Operating System name and version

23. Major Tools Available
 Some of the best and the most commonly used Port
Scanners are:
 Nmap
 Superscan
 Hping
 Nessus
 Common Features of all above Port Scanners:
 Very Easy to Use
 Display Detailed Results
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24. Nmap
 Nmap (Network Mapper) is a security scanner originally
written by Gordon Lyon , (1997).
 Is a free and open source, Website nmap.org.
 Nmap runs on all major computer operating systems
 Used to discover
 hosts and services on acomputer network, and security
auditing
 Thus creating a "map" of the network.
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25. 25
 Determain what..
 operating systems
 vulnerability detection.
 It was designed to rapidly scan large networks
 Nmap is also capable of adapting to network
conditions including latency and congestion during a
scan
 Nmap sends specially crafted packets to the target
host and then analyzes the responses.

26. Nmap features
 Host discovery
 Port scanning
 Version detection
 OS detection
 Nmap can provide further information on targets,
including reverse DNS names, device types, and
MAC addresses.
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27. 27

28. 28

29. 29

30. Anti-Port Scanning
 Some useful Anti-Port Scanning software available
are:
 Scanlogd
 BlackICE
 Snort
 Abacus Port sentry
 And multi tools using to hide the IP address .
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31. Reference
 http://nmap.org/book/man.html
 http://nmap.org/book/install.html
 http://nmap.org/nsedoc
 H.mondo89@yahoo.com
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