Optical DNA

2022

J Cryptogr Eng

Abstract“Classical keys,” i.e., secret keys stored permanently in digital form in nonvolatile memory, appear indispensable in modern computer security—but also constitute an obvious attack target in any hardware containing them. This contradiction has led to perpetual battle between key extractors and key protectors over the decades. It is long known that physical unclonable functions (PUFs) can at least partially overcome this issue, since they enable secure hardware without the above classical keys. Unfortunately, recent research revealed that many standard PUFs still contain other types of “secrets” deeper in their physical structure, whose disclosure to adversaries breaks security as well: Examples include the manufacturing variations in SRAM PUFs, the power-up states of SRAM PUFs, or the signal delays in Arbiter PUFs. Most of these secrets have already been extracted in viable attacks in the past, breaking PUF-security in practice. A second generation of physical security primitives now shows potential to resolve this remaining problem, however. In certain applications, so-called Complex PUFs, SIMPLs/PPUFs, and UNOs are able to realize not just hardware that is free of classical keys in the above sense, but completely “secret-free” instead. In the resulting hardware systems, adversaries could hypothetically be allowed to inspect every bit and every atom, and learn any information present in any form in the system, without being able to break security. Secret-free hardware would hence promise to be innately and permanently immune against any physical or malware-based key-extraction: There simply is no security–critical information to extract anymore. Our survey and tutorial paper takes the described situation as starting point, and categorizes, formalizes, and overviews the recently evolving area of secret-free security. We propose the attempt of making hardware completely secret-free as promising endeavor in future hardware designs, at least in those application scenarios where this is logically possible. In others, we suggest that secret-free techniques could be combined with standard PUFs and classical methods to construct hybrid systems with notably reduced attack surfaces.

Section: Related Workmentioning

confidence: 99%

Secret-free security: a survey and tutorial

2022

J Cryptogr Eng

“…Already prior to PUFs, a side strand of physical security research had suggested (in today's parlance) early forms of secret-free, unforgeable physical tags or labels. These approaches date back to as early as the late 1960s [39], and have resurfaced independently again in the 1980s [3,23], 1990s [10,25,51,52,67,68,79], and 2000s [7,9,11,14,26,71,81]. It seems some of these methods went mostly unnoticed by the larger security community, though; to this day, they are not routinely quoted in the PUF-literature, unfortunately.…”

Section: Related Workmentioning

confidence: 99%

“…Storage media like CDs/DVDs possess unique physical properties on a sub-digital, analog level [26,81], even if they store exactly the same digital content. Building on this observation, any digital content on CDs/DVDs can be certified, again using digital signatures in combination with the physically unique features of each CD [26,81], as in Section 6.4. Customary CD/DVD-readers can then serve as widespread, inexpensive, but surprisingly accurate measurement devices, as demonstrated in [26,81].…”

Section: Secret-free Digital Rights Managementmentioning

confidence: 99%

“…Building on this observation, any digital content on CDs/DVDs can be certified, again using digital signatures in combination with the physically unique features of each CD [26,81], as in Section 6.4. Customary CD/DVD-readers can then serve as widespread, inexpensive, but surprisingly accurate measurement devices, as demonstrated in [26,81]. Both CDs/DVDs and readers are secret-free in this approach, contrary to existing techniques [1].…”

Section: Secret-free Digital Rights Managementmentioning

confidence: 99%

See 1 more Smart Citation

SoK

Proceedings of the 4th ACM Workshop on Attacks and Solutions in Hardware Security

2020

Digital secret keys are indispensable in modern cryptography and computer security-but at the same time constitute a routinely exploited attack target in every hardware system that stores them. This discrepancy has created perpetual battle between key extractors and protectors over the decades. Some recent approaches attempt to overcome this issue by simply avoiding keys and secrets in vulnerable devices: Physical Unclonable Functions (PUFs), for example, are capable of evading "classical keys", i.e., permanently stored digital secrets, in electronic hardware. Nevertheless, many PUFs still contain physical or analog secrets deep in their structure, whose disclosure to adversaries also breaks security: This includes the manufacturing variations in SRAM PUFs that determine their power-up states, or the signal delays of Arbiter PUFs that determine their responses. A second generation of physical primitives shows promise to resolve this remaining problem: Socalled Complex PUFs, SIMPLs/PPUFs, and related techniques enable completely "secret-free" systems, where adversaries could inspect every bit and every atom, and learn any information present in any form in the hardware, without being able to break security. This Systematization of Knowledge (SoK) paper takes this situation as starting point, and categorizes, formalizes, and overviews the recently evolving area of secret-free security. It tries to lay the foundations for future generations of secret-free hardware, which could be innately and provably immune against any invasive, side channel, or key extraction attacks.

“…Again, in combination these features are not met by any comparable technique known to the author. In [38], [39], [40], for example, the random features of the data carrier must be determined in the near-field by analog measurements. The features must be communicated correctly by the analog measurement apparatus (e.g., the optical drive) to a central module (e.g., a TPM) that decides about the validity of the content, meaning that the measurement apparatus must be trusted.…”

Section: B Two Other Applications: Unforgeable Labels and Drmmentioning

confidence: 99%

SIMPL Systems as a Keyless Cryptographic and Security Primitive

Cryptography and Security: From Theory to Applications

2012

Abstract-We discuss a recent cryptographic primitive termed SIMPL system. Like Physical Unclonable Functions (PUFs), SIMPL systems are disordered, unclonable physical systems with many possible inputs and a complex input-output behavior. Contrary to PUFs, however, each SIMPL system comes with a publicly known, individual numeric description that allows its slow simulation and output prediction. While everyone can determine a SIMPL system's output slowly by simulation, only its actual holder can determine the output fast by physical measurement. This added functionality allows new public key like protocols and applications.But SIMPLs have a second, perhaps more striking advantage: No secret information is, or needs to be, contained in SIMPL systems in order to enable cryptographic security. Neither in the form of a standard digital key, nor as secret information hidden in the random, analog features of some hardware, as it is the case for PUFs. The security of SIMPL systems instead rests on (i) an assumption regarding their physical unclonability, and (ii) a computational assumption on the complexity of simulating their output. This provides SIMPL systems with a natural immunity against any key extraction attacks, including malware, side channel, invasive, and modeling attempts.In this manuscript, we give a comprehensive discussion of SIMPLs as a cryptographic and security primitive. Special emphasis is placed on the different cryptographic protocols that are enabled by this new tool.