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11

The paper Enabling Standardized Cryptography on Ultra-Constrained 4-bit Microcontrollers (page 255) describes such an implementation.


9

In summary: the premise "there is so little space in the bootloader that no cryptographically secure decryption algorithm can be implemented there" is likely wrong; thus security-by-obscurity is not the way to go. The method described in the question attempts to "prevent theft from the publicly released update"; but it fails to do that if an adversary ...


8

Yes, AES could be implemented on a 4-bit micro-controller such as this EM6626, and that would not be rocket science or stupidly slow. This application note illustrates that all kind of 8-bit operations are simple, and table lookups are possible. In fact, tables are not even indispensable if performance is non-critical; see this minimalist AES source code in ...


7

Thought I'd begin with some references for you that might be of interest. These terms are used as key 'selling points' for a number of schemes, including many of the CAESAR submissions. Some examples using the terms specifically are given below - most of which are from CAESER because I have the zoo in-front of me: "Online": OCB, Ascon, CBA, APE, NORX ...


7

For your application: "I need the (underpowered 8-bit) slave to be able to tell if a command issued is really trustable", RSA signature with low public exponent ($e=3$), or Rabin (an analog with $e=2$), is likely the most appropriate, assuming you can't trust the slaves to keep a key secret, which is the only realistic assumption unless that slave uses ...


2

Have you considered using symmetric key crypto (MAC) instead ? Elliptic Curve Crypto or even regular (but costly) modular arithmetic might be overkill in your case. As I understand it you would be able to precharge MAC keys into your master and slaves before deployment and you would be set. You can even generate a different key for each so that the ...


1

Someone answered it in another "exchange" site: http://electronics.stackexchange.com/questions/1830/md5-implementation-for-microcontroller There you have links to C implementations, etc. And yes, it's possible to implement MD5 and SHA1 in 8bits, you'll just have to worki with 16 (or 32) bits operations, not that hard...


1

Generally it is not advisable to create your own cryptographic operations on a smart card. When programming a smart card you need to understand the risks of side-channel attacks and perturbation attacks. For instance, you may need to program your way around DPA (Differential Power Analysis) and LFI attacks (Laser Fault Injection). Normally you program on ...



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