Algebraic-side channel attack(ASCA) was proposed by Renauld et al.which combines algebraic attack and side channel attack.The current research of ASCA mainly focuses on the 8-bit implementation of a block cipher.For 64-bit platform

there is no such research.This paper gives an extended algebraic side channel attack which represents the leaked information as explicit function of the key bits.Compared with the original ASCA

the extended ASCA needs less leaked information.As an application

we give an extended ASCA on LBlock light weight block cipher:For LBlock implemented on 64-bit platform

if the Hamming weight of the output of 1-3 round of LBlock can be obtained without error

then with 35 known plaintexts

an equation system concerning the 80 bit maser key can be set up;on a general PC

the 80 bit master key can be obtained in a minute by using Magma mathematical software v2.12-16 to find the Groebner basis.This is the first ASCA attack on LBlock

which shows that the method of moving form 8-bit platform to larger devices suggested by Renauld et al.to prevent ASCA is not enough.