Charm-crypto搭建CP-ABE密码系统

在做毕业设计, 所以顺便把做的实验总结成文章.

CP-ABE原理

另一篇文章总结了

搭建CP-ABE系统

注意必须先确保正确安装了Charm-crypto环境. 安装比较坑, 可以根据我的文章安装.
https://blog.csdn.net/qq_33976344/article/details/115383904

系统结构图

算法
(1) S e t u p ( ) Setup() Setup(): 生成主密钥MK, 公开参数PK. MK是只有算法构造者掌握, PK被所有相同参与者接收
(2) C T T = E n c r y p t ( P K , T , M ) CT_T = Encrypt(PK, T, M) CTT​=Encrypt(PK,T,M): 使用PK, 访问结构T, 将明文M加密为密文 C T T CT_T CTT​
(3) S K S = K e y G e n ( M K , S ) SK_S = KeyGen(MK, S) SKS​=KeyGen(MK,S): 用MK, 用户属性值S生成用户私钥 S K S SK_S SKS​
(4) M = D e c r y p t ( C T T , S K S ) M = Decrypt(CT_T, SK_S) M=Decrypt(CTT​,SKS​): 用户用私钥 S K S SK_S SKS​解密 C T T CT_T CTT​得到明文M, 当且仅当用户属性S满足访问结构T时才能解密成功.

角色

• 可信权威: 维护属性和密钥的对应, 负责执行算法的(1), (3); 持有MK, 同时要为用户分发密钥 S K S SK_S SKS​
• 数据所有者: 通过数据服务者向用户分享数据, 负责定义访问结构T, 执行算法的(2), 加密要分享的数据.
• 用户: 持有可信权威分发的属性密钥 S K S SK_S SKS​, 执行算法(4), 可以解密相应的数据.
• 服务提供者: 只做数据存储功能的提供者, 不参与任何算法执行.

实现系统配置、密钥分发、加密和解密，属性结构树设置，并测试加解密时间. 代码如下:

from charm.toolbox.pairinggroup import PairingGroup, GT
from charm.schemes.abenc.abenc_bsw07 import CPabe_BSW07
from time import *

def Print_Time(T_encrypt: list, T_decrypt1: list, T_decrypt2:list):
    print('Time of Encryption:')
    for _ in range(len(T_encrypt)):
        print(T_encrypt[_], end = ' ')
    print('')
    print('Average time used: ', sum(T_encrypt) / len(T_encrypt), '\n')

    print('Time of Decryption#1:')
    for _ in range(len(T_decrypt1)):
        print(T_decrypt1[_], end = ' ')
    print('')
    print('Average time used: ', sum(T_decrypt1) / len(T_decrypt1), '\n')

    print('Time of Decryption#2:')
    for _ in range(len(T_decrypt2)):
        print(T_decrypt2[_], end = ' ')
    print('')
    print('Average time used: ', sum(T_decrypt2) / len(T_decrypt2), '\n')

def main():
    # instantiate a bilinear pairing map
    pairing_group = PairingGroup('SS512')
    
    # CP-ABE under DLIN (2-linear)
    cpabe = CPabe_BSW07(pairing_group)

    # run the set up
    (pk, msk) = cpabe.setup()

    # generate a secret_key
    attributes = ['ONE', 'TWO', 'THREE', 'FOUR']
    secret_key = cpabe.keygen(pk, msk, attributes)

    # generate a Practitioiner#1 key
    practitioner1_attr_list = ['ONE', 'THREE', 'FOUR']
    practitioner1_key = cpabe.keygen(pk, msk, practitioner1_attr_list)

    # generate a Practitioiner#2 key
    practitioner2_attr_list = ['THREE', 'FOUR']
    practitioner2_key = cpabe.keygen(pk, msk, practitioner2_attr_list)


    # test encryption and decryption time
    # test for 10 rounds

    times_p1 = []
    times_p2 = []
    times_enc = []
    times_dec = []
    Rounds = 10
    policy_str = '((ONE and THREE) and (TWO OR FOUR))'

    for _ in range(Rounds):
        # choose a random message pretend to be owner's record
        msg = pairing_group.random(GT)
    
        # generate a ciphertext
        start_time = time()
        ctxt = cpabe.encrypt(pk, msg, policy_str)
        end_time = time()
        times_enc.append(end_time - start_time)

        # decryption as Owner
        start_time = time()
        rec_msg = cpabe.decrypt(pk, secret_key, ctxt)
        end_time = time()
        times_dec.append(end_time - start_time)
        if rec_msg == msg:
            print ("Successful decryption as Owner.")
        else:
            print ("Decryption as a Owner failed.")

        # decryption as Practitioner
        start_time = time()
        rec_msg = cpabe.decrypt(pk, practitioner1_key, ctxt)
        end_time = time()
        times_p1.append(end_time - start_time)
        if rec_msg == msg:
            print ("Successful decryption as a Practitioner#1.")
        else:
            print ("Decryption as a Practitioner#1 failed.")

        # decryption as Practitioner#2
        start_time = time()
        rec_msg = cpabe.decrypt(pk, practitioner2_key, ctxt)
        end_time = time()
        times_p2.append(end_time - start_time)
        if rec_msg == msg:
            print ("Successful decryption as a Practitioner#2.")
        else:
            print ("Decryption as a Practitioner#2 failed.")
    

    Print_Time(times_enc, times_dec, times_p1)

if __name__ == "__main__":
    main()