State-dependent changeable scan architecture against scan-based side channel attacks

Scan‐based attack tolerance with minimum testability loss: a gate‐level approach

“…This method has very high area overhead, furthermore, the operation of the mask function is not clearly discussed and we believe its testability drop is also high. In [15,16], a -SDSFF has been proposed to dynamically change data of the scan cells for scan chain obfuscation. This method needs a timing controller that is not considered in the security and testability measurements, in fact, if any intentional or natural fault occurs in the controller, the whole chip will lose its testability [17].…”

“…Although details of a hardware implementation of encryption algorithms may affect a success rate of the attack, e.g. whether the algorithm is implemented by pipeline or iterative architectures [9,10,14], the generality of attack helped attackers to break any type of implementation so far [9][10][11][12][13][14][15][16].…”

“…In Table 6, the proposed method is compared with other protecting methods including, MKR [10], round register masking [14], SDFF_100 [16], dynamic obfuscation lock & key [17], onchip comparison [18], PUF-based lock & key [20], dynamic-key [22], DOS [23], and key masking lock & key (ISSATCU) [25] in terms of probability of a successful attack and area overhead. As can be seen in Table 6, the proposed method offers the highest achieved security with the lowest imposed area overhead.…”

“…advanced encryption standard (AES) [10,[12][13][14], data encryption standard (DES) [9,11], and Rivest-Shamir-Adleman [15,16]. On the other hand, there are several countermeasures which attempt to protect crypto-chips against scan-based attacks in different ways such as mirror key register (MKR) [10], round register masking [14], state-dependent scan flip-flop (SDSFF) [15,16], dynamic obfuscation lock & key [17], on-chip key comparison [18,19], physically unclonable function (PUF)-based lock & key [20], dynamic scan [21], dynamic-key [22], dynamic obfuscation scan (DOS) [23], and key masking [24,25]. However, such countermeasures for scan-based attack tolerance suffer from one or more drawbacks which are described in the next section.…”

Don't forget to lock your SIB: hiding instruments using P1687

“…In [17], the flip-flops only capture data if certain bits of the test vectors (hopefully don't care bits) are set to pre-defined values. In [18], some bits in the chain are dynamically inverted depending on previous output values of selected flip-flops, while [19] inserts random inverters before the shift input on some flops to make extraction of information from cryptographic hardware more difficult. In [20] scan data is also selectively changed, but with XORs.…”