PRIDE is a light weight block cipher designed by Albrecht et al.in CRYPTO 2014

which adopts the classical SPN (Substitution Permutation Network) structure and iterates for 20 rounds.The construction of linear layers is very interesting and performances good both in security and efficiency.This paper investigates the properties of the S-boxes and the linear matrices

and then constructs 16 different 2-round iterative linear approximations with the bis 2

-5

and 8 different 1-round iterative linear approximations with the bis 2

-3

.Base on some suitable approximations

attacks on 18-round and 19-round

PRIDE are presented by means of linear cryptanalysis with the properties of key schedule

the linear characteristics and the partial-sum technique

which need about 2

74.9

encryptions with 2

60

known plaintexts and 2

74.9

encryptions with 2

62

known plaintexts

respectively.Furthermore

some interesting links between differential and linear characteristics are shown

which are helpful to reduce the compute complexity.Our analysis is the first linear attack on PRIDE block cipher with known plaintexts.