Efficient Searchable Symmetric Encryption Supporting Dynamic Multikeyword Ranked Search

Table 2

Notations.

F	A document set {f1, f2, …, fn}.
n	The number of documents in F.
C	The encrypted form of F, denoted by {c1, c2, …, cn}.
Wi	The keyword set {, ,…, } for the document fi.
ti	The number of keywords in Wi, and .
	The jth keywords in Wi, and , .
	The vector representation for Wi.
	The vector representation for .
u	A node in the index tree.
	The vector representation for the node u.
,	Vector representations are obtained by splitting .
Iu	The encrypted index for the node u.
IT	The encrypted index tree of F.
Q	The keyword set, {q1, q2, …, qt}, for query.
qj	A keyword in Q, .
	The vector representation for query Q.
,	Vector representations are obtained by splitting .
	The vector representation for qj.
TQ	The trapdoor of Q.
D	A dictionary, {, , …, }, containing all keywords in F.
M11, M12, M21, M22	Matrices for encryption (encryption key).
, , ,	Matrices for decryption (decryption key).
N	The number of semantic keywords associated with each dictionary’s keyword.
m	The number of keywords in D.
d	The dimension of vector generated by using “Word2vec.”
k	The number of files returned to the user.