openpgp message format

Java Privacy Guard

An Implementation of theOpenPGP Message Format in Java

Stefan More,Advisor: Dieter Bratko, Peter Lipp

June 13, 2014

Overview

1. Problem Statement

2. openPGP

3. Java Privacy Guard

4. Summary & Outlook

Stefan More, Bakk@IAIKJune 13, 20142

Problem Statement

Message Confidentiality

Message Integrity

Sender Authentication

Anonymity

End to End


openPGP


PGP History

Pretty Good Privacy

1991: PGP created by Phil Zimmermann

most widely used email encryption software [6]

1998: PGP 5 standardized: openPGP (RFC 4880)

2010: PGP assets sold to Symantecfor $ 300.000.000 (Enterprise Security)


Standard: openPGP (RFC 4880 etc.)

Implementations:

PGP (Zimmermann, Symantec)GnuPG / GPG (GNU)APG (Android)End-to-End (Google Chrome)Bouncycastle (Java)Java Privacy Guard (IAIK-JCE)


openPGP

Combines Symmetric-Key Cryptographyand Public-Key Cryptography

+ Hashing

+ Data Compression

+ Trust Model


Revisiting Problem Statement

Message Confidentiality: Encryption

Message Integrity: Digital Signatures

Sender Authentication: Web Of Trust

Anonymity? Tor, I2P, . . .


De-/Encryption

Encrypt Data with Random Symmetric-Key,encrypt Symmetric-Key with Public-Key

Multiple Receiver: Encrypt Data only once

Symmetric Cipher: AES, IDEA, 3DES, CAST5, . . .Keysize ≥ 112 bits [7]

Public-Key Cipher: RSA, ElGamalKeysize ≥ 2048 bits [7]


Digital Signatures

Hash Message Body & Sign Hash with Private Key

Sign Other Keys (→ Trust Model)

Hash Algorithms: SHA-2, SHA-1, RIPE-MD/160, MD5

Signature Algorithms: RSA, DSA


Web Of Trust

Decentralized Trust Model(Can be centralized)

No Certificate Authority

Transitive Trust

Pathfinder: pgp.cs.uu.nl/doc/faq.html

Key-Set Analysis: pgp.cs.uu.nl/plot


pgp.cs.uu.nl/doc/faq.html

pgp.cs.uu.nl/plot

Java Privacy GuardopenPGP in Java using IAIK-JCE


Java Privacy Guard

Full Implementation of RFC 4880 (not yet)

Compatibility to other PGP Implementations

Simple API & Extended API

Key Management

Crypto provided by JCA (default: IAIK-JCE)


openPGP Structure

Packets:

Internal StructureContain actual Data (+ Metadata)

Transferable:

Consists PacketsMessage, Keys, Signature, Keyring, . . .


tag: Public-Key EncryptedSession Key Packetlength: 526version: 3keyId:“9BF7B564D09AFB49”publicKeyAlgorithm:“Elgamal (Encrypt-Only)”encryptedSessionKey

tag: Public-Key EncryptedSession Key Packetlength: 524version: 3keyId:“B5801FD826746039”publicKeyAlgorithm:“RSA (Encrypt or Sign)”encryptedSessionKey

tag: Symmetrically Encrypted Data Packetlength: 33Encrypted Data


Load & Decrypt PGP Message

IAIK . addAsProvider ( ) ;

PGPMessage pgpMessage = parseMessage ( i s1 ) ;PGPPrivateKey pr ivKey = parsePr ivatekey ( i s2 ) ;

PGPCipher c ipher = new PGPCipher ( ) ;c ipher . i n i t ( PGPCipher .DECRYPT MODE, p r i vkey ) ;

byte [ ] c l e a r t e x t = c ipher . doFina l ( pgpmessage ) ;


Summary

Studied RFC 4880 & IAIK-JCE

Implemented:

Reading ASCII-Armor (Base 64 + CRC24)Parsing PGP Message Objects (Packets)Key Management (Simple Keychain)Message Decryption (RSA & ElGamal)Signature Validation (RSA & DSA)Decompression


Outlook / Future Research

Message Encryption and Signature Validation

Missing parts of RFC 4880 (Partial body length, . . . )

RFC 6637: ECC

Keyservers?


Thank You for Your AttentionQuestions? Remarks?


[1] Laura Poitrashttps://commons.wikimedia.org/wiki/File:Edward_Snowden-2.jpg

[2] Glenn Greenwald https://en.wikipedia.org/wiki/File:Glenn_greenwald_portrait_transparent.png

[3] Katy Scogginhttps://commons.wikimedia.org/wiki/File:Laura_Poitras_2014.jpg

[4] Regionales RechenZentrum Erlangenhttps://commons.wikimedia.org/wiki/Category:RRZE-Icon-Set

[5] The Opte Project http://www.opte.org/the-internet

[6] http://www.philzimmermann.com/EN/background/index.html

[7] Recommendation for Key Management, Special Publication 800-57 Part 1Rev. 3, NIST, 07/2012. http://www.keylength.com/en/4/

[8] http://cirw.in/gpg-decoder


https://commons.wikimedia.org/wiki/File:Edward_Snowden-2.jpg

https://en.wikipedia.org/wiki/File:Glenn_greenwald_portrait_transparent.png

https://en.wikipedia.org/wiki/File:Glenn_greenwald_portrait_transparent.png

https://commons.wikimedia.org/wiki/File:Laura_Poitras_2014.jpg

https://commons.wikimedia.org/wiki/Category:RRZE-Icon-Set

http://www.opte.org/the-internet

http://www.philzimmermann.com/EN/background/index.html

http://www.keylength.com/en/4/

http://cirw.in/gpg-decoder

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openpgp message format

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