ABYSS : An Architecture for Software Protection

1
ABYSS An Architecture for Software Protection

• IEEE Transactions on Software Engineering
• June 1990
• Steve R. White and Liam Comerford
• Jaewon Lee

2
Introduction

• Traditional S/W protection method
• writing in unusual way
• copy protection by feature on the distribution
  diskette
• attachment of special H/W devices
• Problem
• both logically and physically open system
• unacceptable burdens on the legitimate user
• Exploration
• physically secure tamper-resistant modules
• cryptographic approach
• crypto-microprocessor

3
Overview of ABYSS

• A Basic Yorktown Security System
• guarantees to execute exactly as it was written
• cannot be modified arbitrarily by the user
• the only encryption and decryption keys must be
  kept secret
• need physically secure device

4
Architecture of ABYSS
Unprotected Processes
Protected Processes
High Privilege Supervisor Process
Unprotected Part of Application 1
Protected Part of Application 1


Right-To- Execute Storage
Protected Part of Application N
Unprotected Part of Application N
Authorization Process
5
Protected Processors

• Minimal, but complete, computing system
• processor
• real-time clock
• random or pseudo-random number generator
• memory
• logically, physically, and procedurally secure
  unit
• Supervisor process
• ensuring the logical and procedural security of
  the protected processor
• cryptographic facility

6
S/W Partitioning

• Protected parts
• encrypted
• only decrypted when it is loaded into protected
  processor
• physically secure while inside the protected
  processor
• cryptographically secure while outside

7
Tokens

• New authorization mechanism
• queries
• generated randomly by protected processors
• sufficiently numerous that no collision
• different queries generate different responses
• responses
• sufficiently numerous that a correct random
  guessing is improbable
• sufficiently independent of each other
• token data is erased from the token as it is read

8
How Tokens Work
Query Line
Query UP
?
1
2
3
n
Up Down
0
Response Line
0
Query Line
?
2
3
4
n
Up Down
0
1
1
1
?
1
0
Response Line
Response 0
0
9
Attacks on The System

• Plaintext software
• Cryptanalytic attacks
• nonchosen plaintext attack
• Physical attacks
• On trusting the H/W manufacturer

10
New Capabilities

• Technical enforcement of terms and conditions
• Protection of distribution channels

11
Conclusion

• ABYSS enables the protected execution of
  application on protected processors
• logical, physical, and procedural security
• S/W is separated from its Right-To-Execute
• Doesnt require changes to S/W distribution
  methods