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Salting as a Countermeasure against Attacks on Privacy Preserving Record Linkage Techniques

: Privacy-preserving record linkage (PPRL) is the research area dedicated to linking records from multiple databases for the same patient without revealing identifying information during the linkage. A popular PPRL approach is based on Bloom ﬁlters (BF). Recent research has shown that BF based PPRL could be vulnerable to cryptanalysis attacks. Among several hardening techniques, salting was considered to be one of the most suitable defences. A thorough evaluation of the amount of protection provided by salting is lacking from the literature. In this paper, we empirically evaluate the effect of salting on privacy by demonstrating the resilience of salted BF to the two most advanced attack methods: pattern mining and graph-matching. Experimental results show that salting could improve resilience against both attacks, although more minor against graph-matching attacks than pattern mining attacks.