physically unclonable function

2.  What is PUF
 History of PUF
 Why we use PUF
 Conclusion
 References

3. Why we use PUF?
PUF can also be use for key generation and
storage this is much more secure than
showing key memory because key in the
memory is vulnerable for physical attack and
other attack but if we use PUF to generate a
key, and PUF generate random output for the
same input

4. Challenges=>Conventional
Authentication
 Conventional Authentication Schemes
 Need to store keys
 Power and area consuming

5. Challenges => Store Secrets
 Conventional approach to embed secure secrets in IC
• Non-volatile memory(ROM, Fuse, Flash or EEPROM)
• Battery-backed RAM
 Non-volatile memory technologies are often vulnerable to invasive
and non-invasive attack
 Adversaries can physically extract secret keys from EEPROM while
processor is off

6. Challenges=>expensive tamper proof
packs
 Storing digital information in a device in a way that is
resistant to physical attacks is difficult and expensive.
IBM 4758
● Tamper-proof package containing a
secure processor which has a secret
key and memory
● Tens of sensors, resistance,
temperature, voltage, etc.
● Continually battery-powered
● ~ $3500 for a 99 MHz processor and
128MB of memory

7. Challenges=>Power and Area
 Power and Area are critical
RFID tag can afford a maximum of 2000 gates for
security features
 Passive RFIDs
 A good cryptographic primitive should be
lightweight, occupy little area on silicon and
should have very low power consumption.

8. What is PUF
 PUF stands for the Physical Unclonable
Function.
 A Physical Unclonable Function, or PUF, is a
"digital fingerprint" that serves as a unique
identity for a semiconductor device such as a
microprocessor.
 PUFs are based on physical variations which occur
naturally during semiconductor manufacturing,
and which make it possible to differentiate
between otherwise identical semiconductors.

9.  PUFs are usually utilized in cryptography.
 A physical unclonable function (sometimes
also called physically unclonable function) is a
physical entity that is embodied in a physical
structure.
 Today, PUFs are usually implemented
in integrated circuits and are typically used in
applications with high security requirements.

10.  PUFs depend on the uniqueness of their
physical microstructure. This microstructure
depends on random physical factors
introduced during manufacturing.
 These factors are unpredictable and
uncontrollable, which makes it virtually
impossible to duplicate or clone the structure.

11. • PUF is based on physical system
• Behaving like random function(that is
generating random output values)
• Unpredictable even for an attacker with
physical access to the system
• Uncloneable or irreproducible o9n other copy
• Of the some physical system even when the
functionality is known.

12. Types of PUFs
o Optical PUFs
o Coating and Acoustic PUFs
o Silicon PUFs(SPUF)
o timing and delay information
o easy integrate into ICs

13. Applications of PUF
1) Low cost authentication[1]

14. Applications of PUF
2) Cryptographic Key Generator[1]

15. Applications of PUF
3) Software Licensing and Anonymous Computation[3]

16. Applications of PUF
3) Software Licensing and Anonymous Computation

17. Applications of PUF
• 4) Random Number Generation [2]
0.1% of all challenges do not return a
consistent response
These meta-stable challenges
generate responses which can vary
unpredictably

18. ● Strong PUFs
○ Large number of challenge response pairs
○ IC identification and secret key generation
○ E.g arbiter PUF and feed forward arbiter
● Weak PUFs
○ Limited number of challenge response pairs
(sometime just single)
○ Secret key generation
○ E.g SRAM PUF and butterfly PUF
Classification of PUFs

19. Using a PUF as an Unclonable Key
• A Silicon PUF can be used as an unclonable key.
• The lock has a database of challenge-response pairs.
• To open the lock, the key has to show that it knows the response to one or
more challenges.
?

20. Private/Public Keys
If a remote chip stores a private key, Alice can share a secret
with the chip since she knows the public key corresponding
to the stored private key
Encrypt Secret using chip’s public key
Only the chip can decrypt Secret using the stored private key
Private Key
Decrypt Secret
Chip
EPublic Key(Secret)

21. Applications
• Anonymous Computation
Alice wants to run computations on Bob’s
computer, and wants to make sure that she
is getting correct results. A certificate is
returned with her results to show that they
were correctly executed.
• Software Licensing
Alice wants to sell Bob a program which will
only run on Bob’s chip (identified by a PUF).
The program is copy-protected so it will not
run on any other chip.
How can we enable the above applications by trusting only a
single-chip processor that contains a silicon PUF?