30-03-2011, 11:28 AM
Presented by
Netiva Caftori
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a digital data encryption program
A word about PGP one of the strongest encryption tools available
Encryption is the process whereby codes are used to attempt to conceal the meaning of a message
Cryptography is the science of writing messages in secret codes . It is about the right to privacy, freedom of speech, freedom of political association, freedom of the press, freedom from unreasonable search and seizure, freedom to be left alone
to promote awareness of the privacy issue in a digital age
Where did PGP come from and how does it work?
PGP is the culmination of a long history of cryptographic discoveries.
PGP uses public and private Key encryption
you'll share your Public Key with anyone you wish
Your Public Key is used to encrypt a message
you'll guard your Private Key secret
The Private Key is used to decrypt data that have been encrypted using your Public Key.
Public and Private Key encryption
the message encrypted using your Public Key can only be decrypted by you, the owner of the corresponding Private Key
encryption solves 1of 2 major problems with older methods, namely that you had to somehow share the key with anyone you wanted to be able to read (decrypt) your secret message
The second major problem with older methods
Unlike earlier encryption methods, the security of PGP encryption lies entirely with the key.
It is PGP's selection of the complex keys used to do an encryption that makes it next to impossible to crack.
Key attributes of Secret key vs. Public key
Thousands years use
DES
Fast
Keys shared between usually only 2 people
128 bit
No non-repudiation (need 3rd party as witness)
Less than 50 years
RSA
Slow
Private: concealed
Public: widely shared
1,024
Nonrepudiation: Can’t deny having sent a message
Vocabulary, definitions, and acronyms
Symmetric encryption
Asymmetric encryption
Plaintext
Cyphertext
Cryptanalyst
Fi(n)=# positive integers <n relatively prime to n
DES=Data Encryption Standard
NSA=National Security Agency
Authentication
Man-in-the-middle
Trapdoors
Key escrow
Brute force attack
Public key encryption systems
1976: Diffie and Hellman
Merkle-Hellman Knapsacks
1978: Rivest-Shamir-Adelman (RSA)
1984: El gamal and digital signature
Hash algorithm
RSA Encryption
operates with arithmetic mod n
e=encryption key; d=decryption key
P=plaintext---> Pe mod n =cyphertext
(Pe)d mod n = P recovered plaintext
Encryption and decryption are mutual inverses and commutative
Select large n=pq p & q prime
Choose e relatively prime to (p-1)(q-1)
Select d so e*d=1 mod (p-1)(q-1)
Or e*d=1 mod fi(n) as fi(p)=p-1 for p prime
Euler-Fermat: x**fi(n)=1mod n for all x relatively prime to n
Simple knapsack example
Public key cryptography is based on multiplicative inverses
Suppose message to encrypt is ABC
Translate to 23+69+14=106
106 is sent
Since 23*22=1 mod 101 the recipient will multiply 106x22=2332=9 mod 101
And infer that the message is ABC since 9=1+3+5
An interceptor will spend a long time figuring it out.
RSA vs. Knapsack
An error was discovered in the knapsack encryption by Shamir (from RSA), and is no longer used.
Modular inverse pairs are more used in RSA than in Knapsack.
RSA is the most widely used public key cryptographic system.
It bases its security on the difficulty of performing inverse calculations.
PGP is a remarkable phenomenon that provides confidentiality, authentication, and compression for email and data storage.
Its building blocks are made of the best available cryptographic algorithms: RSA, DSS, Diffie-Hellman.
It is independent of operating system and processor.
It has a small set of easy-to-use commands
Conclusions
Because PGP is freely available via the Internet, and has a fully compatible low-cost commercial version it is now widely used.
It has a wide range of applicability from corporations to individuals who wish to communicate worldwide securely over the Internet and other networks.
It is not controlled by any government which makes it attractive to many.
