1. A method of establishing public key cryptographic protocols against the quantum computational attack, comprising a method for generating a shared key, wherein the method for generating a shared key comprises the following steps: (11) establishing an infinite non-abelian group G and two subgroups A and B of G, so that for any a ∈A and any b∈B, the equation ab=ba is true; (12) choosing, by a first entity of a protocol, an element g in G, wherein the first entity of the protocol chooses two elements b 1 , b 2 ∈A as private keys, and a second entity of the protocol chooses two elements d 1 , d 2 ∈B as private keys; (13) choosing, by the second entity of the protocol, two elements c 1 , c 2 ∈B, computing y=d 1 c 1 gc 2 d 2 , and sending y to the first entity of the protocol; (14) choosing, by the first entity of the protocol, four elements a 1 , a 2 , b 3 , b 4 ∈A, computing 
 x=b 1 a 1 ga 2 b 2 and z=b 3 a 1 ya 2 b 4 =b 3 a 1 d 1 c 1 gc 2 d 2 a 2 b 4 , and sending (x, z) to the second entity of the protocol; (15) choosing, by the second entity of the protocol, two elements d 3 , d 4 ∈B, computing 
 w=d 3 c 1 xc 2 d 4 =d 3 c 1 b 1 a 1 ga 2 b 2 c 2 d 4 
 and 
 v=d 1 − zd 2 −1 =d 1 −1 b 3 a 1 d 1 c 1 gc 2 d 2 a 2 b 4 d 2 −1 =b 3 a 1 c 1 gc 2 a 2 b 4 and sending (w, v) to the first entity of the protocol; (16) computing, by the first entity of the protocol, 
 u=b 1 −1 wb 2 −1 =b 1 −1 d 3 c 1 b 1 a 1 ga 2 b 2 c 2 d 4 b 2 −1 =d 3 c 1 a 1 ga 2 c 2 d 4 , and sending u to the second entity of the protocol; and (17) computing, by the second entity of the protocol, K B =b 3 −1 vb 4 −1 =a 1 c 1 gc 2 a 2 , and computing, by the second entity of the protocol, K B =d 3 −1 =c 1 a 1 ga 2 c 2 ; because a 1 , a 2 ∈A, and c 1 , c 2 ∈B, a 1 and c 1 are separately commute with a 2 and c 2 in multiplication, so that the first entity of the protocol and the second entity of the protocol reach a shared key K=K A =K B .