Analysis and Evaluation of Schemes for Secure Sum in Collaborative Frequent Itemset Mining across Horizontally Partitioned Data

Algorithm 2

Proposed algorithm for secure sum in PPDFIM using symmetric keys.

Setup: Each party exchanges its seed with the STTP securely.

( is the plain text at the th party) (); ; .

Frequentitems = .

Require: .

(1) for each global candidate itemset = 1 to

(2)  for each party (

   Encryption phase:

(3)  Each party has a secret where is the modulus

(4)  Each party generates a key stream where is the modulus

(5)  Ciphertext mod

(6)  end for

   Aggregation:

(7)  cipherSum = 0

(8)     for   = 1 to

(9)     cipherSum = cipherSum + mod

(10)    sends cipherSum to

(11)   end for

    Decryption at STTP:

(12)   Sum = cipherSum

(13)   Sum = Sum − mod

(14)    broadcasts the value of Sum to all the parties

(15)   if (Sum > global support threshold)

(16)   Frequentitems = Frequentitems Itemset

(17) end for

(The same procedure is followed for finding the frequent association rules

once the frequent itemsets are deciphered in case of PPDARM.)

^* sends the sum value to which is a semi-honest trusted third party (STTP).

(i) If Sum = > , decryption produces Sum < . In practice, must be chosen as .