Description of basic workings of PGP

1. pretty good privacy securing e-mail communication 5.5.2010

2. THE PROBLEM e-mail „security“ 5.5.2010 Pretty good privacy 2

3. SMTP protocol 5.5.2010 3 S: 220 smtp.example.com ESMTP Postfix C: HELO relay.example.org S: 250 Hello relay.example.org, I am glad to meet you C: MAIL FROM:<bob@example.org> S: 250 Ok C: RCPT TO:<alice@example.com> S: 250 Ok C: RCPT TO:<theboss@example.com> S: 250 Ok C: DATA S: 354 End data with <CR><LF>.<CR><LF> C: Hello Alice. C: Your friend, Bob C: . S: 250 Ok: queued as 12345 C: QUIT S: 221 Bye Pretty good privacy

4. SMTP protocol 4 PLAIN TEXT everyone on the way can read it Pretty good privacy 5.5.2010

5. SMTP protocol Pretty good privacy 5 NO AUTHENTICATION everyone can pose as everyone 5.5.2010

6. SMTP protocol Pretty good privacy 6 SIZE LIMIT e-mails are limited in size 5.5.2010

7. THE SOLUTION PGP - open solution to our problems 5.5.2010 Pretty good privacy 7

8. PGP features Authentication Confidentiality Compression Segmentation 8 5.5.2010 Pretty good privacy

9. Predicates Asymetric encryption Digest algorithm 9 Private/public key pair Private key is secret and uncompromised Private key encrypted data can only be decrypted by corresponding public key Reverse holds true as well Same input always generates same output Small change of input causes huge change on output Chance of collision has to be minimal 5.5.2010 Pretty good privacy

10. Authentication 10 confirming the sender‘s identity MATCH? SHA-1digest SHA-1digest Sender‘s public key RSAencryption RSAdecryption Sender‘s private key 5.5.2010 Pretty good privacy

11. Encryption 11 confirming the sender‘s identitymaking sure noone else can read the message IDEAencryption Session key IDEAencryption Recipient‘s public key 5.5.2010 Pretty good privacy

12. Decryption 12 confirming the sender‘s identitymaking sure noone else can read the message IDEAdecryption IDEAdecryption Session key Recipient‘s private key 5.5.2010 Pretty good privacy

13. Decryption 13 saving bandwidthincreasing cryptoanalysis resistance Sender Recipient 5.5.2010 Pretty good privacy

14. Compatibility & segmentation 14 traveling across platformsavoiding maximum size limit Compatibility +33% size radix-64 binary data Segmentation automatic segmentation and reassembly of long messages 5.5.2010 Pretty good privacy

15. THE CONCLUSION Jernej Virag 15 5.5.2010 Pretty good privacy