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Public Key Encryption
IntroductionIntroduction
The Problem Network security
Encryption/Decryption
Public Key Encryption How is data transmitted? Secure Socket Language
Conclusion Questions and Comments
The ProblemThe Problem
Trough the Internet, people can:
Buy products onlineBuy services onlineDo bank transactions online
The ProblemThe Problem
Threats to network security include: Data diddling Salami attack Piggybacking Denial of Service (DoS) Distributed Denial of Service (DDoS)
The ProblemThe Problem
Several network security schemes have been developed and used throughout the years
Network SecurityNetwork Security
Protection alternatives include:
Use of passwordsUse of security modemsEncryption/decryption methods
Network SecurityNetwork Security
The most secure protection methods are those which use
Encryption / DecryptionEncryption / Decryption
Network SecurityNetwork SecurityHistory
Used since Roman Empire
Used by governments for military purposes
Nowadays it is being performed by computers
History
Network SecurityNetwork SecurityWhat is encryption/decryption?
"Enryption is the translation of data into a secret code."
Encryption / Decryption
Network SecurityNetwork SecurityWhat is encryption/decryption?
Transposition AlgorithmTransposition Algorithm
An exampleAn example
Network SecurityNetwork Security
Key = PUBLICPUBLIC
What is encryption/decryption?
P U B L I C
5 6 1 4 3 2
Network SecurityNetwork SecurityWhat is encryption/decryption?
Message to send:
Public key encryption is secure now
Network SecurityNetwork SecurityWhat is encryption/decryption?
5 6 1 4 3 2
P U B L I C
K E Y E N CR Y P T I O
N I S S E C
U R E N O W
B Y P
Network SecurityNetwork SecurityWhat is encryption/decryption?
The message will now be …
BYPSE CCOCF INIEF LETSF PKRNU UEYIR
Unauthorised users who do not have the key will not be able to convert it back to the original message
Network SecurityNetwork SecurityWhat is encryption/decryption?
Decryption is the changing back of encrypted code (or cipher text) to plain text.
A key or password is necessary for encryption and decryption.
Network SecurityNetwork SecurityWhat is encryption/decryption?
Network SecurityNetwork Security
There are two main types of encryption / decryption security measures:
Public Key Encryption (Asymmetric)
Symmetric Key Encryption
What is encryption/decryption?
Network SecurityNetwork SecurityPublic Key (Asymmetric) EncryptionPublic Key (Asymmetric) Encryption
Uses two keys:
Public
Private A popular implementation is the
SSL (Secure Socket Layer)
Public Key Encryption
Network SecurityNetwork SecuritySymmetric Key Encryption
Uses only one key
Key must be known only by the
sender and receiver
Faster encryption/decryption
Symmetric Key
Public Key EncryptionPublic Key Encryption
First invented in early 1970s by Clifford Cocks.
Reinvented by Rivest, Shamir and Adleman in 1976 and was called RSA. It was published.
In 1984 ElGamal created his algorithm. In 1989 Koblitz created his hyperelliptic curve
cryptography algorithm
History
Public Key EncryptionPublic Key Encryption
Sender encrypts the message
using its private key
Sender encrypts its private key
using the receiver’s public key
How is data sent How is data sent using public key using public key
encryption?encryption?
Receiver uses its private key to
decrypt the sender’s private key
Receiver uses the sender’s private
key to decrypt the message.
How is data sent?
Public Key EncryptionPublic Key Encryption
Authentication is also done using digital signatures.
Digital signatures are sent to the receiving computer to make sure that the sender is who it says it is.
Digital signatures
Public Key EncryptionPublic Key Encryption
Digital certificates are used.
Before communication starts the certificate authority confirms that every computer is who it says it is.
A large scale
Public Key EncryptionPublic Key Encryption
Hashing algorithms are used to create keys.
A simple example:
Hashing algorithms
Input number
Hashing Algorithm
HashValue
32,569 Input # x 138 4,494,522
Public Key EncryptionPublic Key Encryption
If the algorithm is not known, it is very difficult to determine the input number.
In reality more complex numbers are used, usually 40-bit or 128-bit
Hashing algorithms
Public Key EncryptionPublic Key Encryption
Checks for data corruption
Two popular algorithms:ChecksumCyclic Redundancy check (CRC)
Validation and Verification of data
Public Key EncryptionPublic Key Encryption
An implementation of Public key encryption
Developed by Netscape
Used extensively by Netscape and Internet explorer
Secure Socket Layer (SSL)
Public Key EncryptionPublic Key Encryption
URL of an SSL-enabled website starts with https://
An example is the Go Mobile page for topping up your mobile credit
Secure Socket Layer (SSL)
Public Key EncryptionPublic Key Encryption
It has become part of the transport layer in the OSI Model
Is known as the TLS (Transport Layer Security)
Secure Socket Layer (SSL)
Public Key EncryptionPublic Key Encryption
Sender creates a private key
Sender sends it to the receiving computer using the receiver’s public key
What happens in an SSL?
Public Key EncryptionPublic Key Encryption
Communication is then encrypted/decrypted using the private key
After communication between the two computers ends the key is discarded
What happens in an SSL?
ConclusionConclusion
The most common protection alternatives used are those that use the encryption/decryption methods.
Encryption is the translation of data into a code that is not understandable without the key.
Decryption is the changing back of code from cipher text to plain text.
A key or password is necessary.
ConclusionConclusion
There are two types:Public key encryptionPrivate / Symmetric key
Private key encryption uses only one key, which is private.
Public key encryption uses two keys: Public keyPrivate key
ConclusionConclusion
How is data sent using public key encryption?
ConclusionConclusion
Authentication is done using digital signatures Digital certificates are used in a large scale
communication Hashing algorithms are used to create keys
and passwords. Checksum and CRC are used to check for
data corruption
ConclusionConclusion
SSL is an implementation of public key encryption.
Private keys are created before every communication session, and deleted afterwards
Visit www.geocities.com/publickeyencryption
For notes and references for further reading