Pretty good privacy

pretty good privacy
securing e-mail communication
5.5.2010

THE PROBLEM
e-mail „security“
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Pretty good privacy
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SMTP protocol
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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

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

SMTP protocol
Pretty good privacy
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NO AUTHENTICATION
everyone can pose as everyone
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SMTP protocol
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SIZE LIMIT
e-mails are limited in size
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THE SOLUTION
PGP - open solution to our problems
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PGP features
Authentication
Confidentiality
Compression
Segmentation
8
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Pretty good privacy

Predicates
Asymetric encryption
Digest algorithm
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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
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Pretty good privacy

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

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

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

Decryption
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saving bandwidthincreasing cryptoanalysis resistance
Sender
Recipient
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Pretty good privacy

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

THE CONCLUSION
Jernej Virag
15
5.5.2010
Pretty good privacy

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Pretty good privacy

by Jernej Virag

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