# Research on a Random Mask Infection Countermeasure against Double Fault Attacks
###### Abstract  
The infection countermeasure, in which the main idea is to prevent adversaries from exploiting faulty ciphertexts to break the key by spreading the induced fault, is a very effective countermeasure against fault attacks. However, most existing infection countermeasures struggle to defend against double-fault attacks effectively due to the single-fault assumption. By analyzing the principle of infection mechanism and adding different random Boolean masks in the two encryption paths, this paper proposes a measure called a random mask infection countermeasure to defend against double-fault attacks. In addition, the multiplication mask is used to randomize the fault diffusion to further resist single-byte fault attacks. The experimental results indicate that the random mask infection countermeasure proposed can perform fault diffusion effectively when the cryptographic circuit suffers double-fault attacks, and the fault diffusion shows randomness, and can effectively defend against these fault attacks. AES; infection countermeasure; mask; fault attacks +
Footnote †: journal: Applied  
1 Xinglin College, Nantong University, Nantong 226236, China; [EMAIL_ADDRESS]  
2
Footnote 1: email: {xinglin.c.ww,  
mechanism in [25] was deficient due to the same unknown mask being used in the infection process and improved on [25]. In 2019, by utilizing the encryption/decryption circuit, [22] proposed a countermeasure against fault attack called random infection mechanism. Since most of these existing countermeasures against fault attacks assume a single-fault condition, i.e., the assumption that only one of the two concurrent circuits employed (e.g., two identical cryptographic circuits) will be injected with a fault [16; 23], thus, it is difficult to defend against double-fault attacks. Although it is difficult to inject the same fault for both encryption or decryption paths (in other words, it is difficult to perform a double-fault attack), with the development of fault injection accuracy, it has become possible to inject double faults [27]. Fortunately, researchers have recognized the threat of double-fault attacks and have discussed them to some extent [22; 24; 28; 29]. In [24], when analyzing existing methods against fault attacks, the possibility of double-fault attacks on cryptographic circuits is clearly stated, but no specific countermeasure is given. In 2016, [PERSON] et al. first systematically analyzed the problem of double-fault attacks in the fault injection phase, constructed a fault injection model, and analyzed how to reduce the difficulty of double-fault injection in the fault injection phase and discussed how to effectively defend against double-fault attacks [28]. Immediately afterward, [PERSON] et al. proposed a fault propagation method using encrypted/decrypted circuits to resist double-fault attacks and analyzed the fault depth with good results [22]. In [29], the authors proposed the concept of a second-order infection mechanism to counter the threat of double-fault attacks by constructing a three-strip cryptographic circuit, which increases the circuit area by approximately half compared to the traditional infection mechanism due to the use of a three-strip cryptographic circuit and the risk of higher fault (e.g., triple-fault) attacks. In view of the serious threat of fault attacks to cryptographic circuits, and the shortcomings of existing infection mechanisms against double-fault attacks, and the fact that the infection mechanism has a single diffusion mode and cannot resist single-byte faults, this paper proposes an infection countermeasure based on random masks. Furthermore, to defend against possible single-byte fault attack, a random multiplication mask also is proposed to be used in the fault diffusion to achieve the purpose of randomizing the fault diffusion.