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 Problem Exploration
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 … …
Part of
Application 1
High
Privilege
Supervisor
Process
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
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 responses
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 Up Down 1  Response Line 12 3 n Up
Down 1 
Response Line 1 
Query Line  2 3 4 n Up
Down 1 1 1  1
Response Line
Response = 0 1 

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
Doesn’t require changes to S/W distribution methods