区块链中 非对称加密通信的大致过程

场景：

A要给B发信息。使用非对称加密，A的公钥为A_public, 私钥为A_private;   B的公钥为B_public, 私钥为B_private。

A要发送的信息为msg。

过程：

1.   A 对要发送的信息msg求出 hash值（msg_hash）,  对求出的 msg_hash 使用A的私钥加密获得加密签名后的hash值为 A_cry_msg_hash。

2.   将  A_cry_msg_hash 与  msg 拼接获得   A_cry_msg_hash+msg 。

3.   使用  B的公钥加密签名   A_cry_msg_hash+msg  获得   B_cry(A_cry_msg_hash+msg),  并将其发送给B。

4.   B获得  B_cry(A_cry_msg_hash+msg)  ，使用B的私钥解密获得  A_cry_msg_hash+msg  。

5.   B 求出msg的hash值 B_msg_hash   ,  使用A的公钥解密 A_cry_msg_hash 获得  msg_hash,  如果 B_msg_hash 等于 msg_hash  则信息没有被篡改。

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图来自于   《Learn Blockchains by Building One》

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部分展示代码：

需要安装pynacl库：

pip install pynacl

from nacl.public import PrivateKey, Box

# Generate Bob's private key, which must be kept secret
bobs_secret_key = PrivateKey.generate()
alices_secret_key = PrivateKey.generate()
print(bobs_secret_key)
print(type(bobs_secret_key))

# Bob's public key can be given to anyone wishing to send Bob an encrypted message
bobs_public_key = bobs_secret_key.public_key
# Alice does the same and then Alice and Bob exchange public keys
alices_public_key = alices_secret_key.public_key
print(bobs_public_key)
print(type(bobs_public_key))

# Bob wishes to send Alice an encrypted message so Bob must make a Box with his private key and Alice's public key
bobs_box = Box(bobs_secret_key, alices_public_key)
print(bobs_box)
print(type(bobs_box))

# This is our message to send, it must be a bytestring as Box will treat it
#   as just a binary blob of data.
secret_message = b"I am Satoshi"
encrypted = bobs_box.encrypt(secret_message)
print(encrypted)
print(type(encrypted))

# Alice creates a second box with her private key to decrypt the message
alices_box = Box(alices_secret_key, bobs_public_key)

# Decrypt our message, an exception will be raised if the encryption was
#   tampered with or there was otherwise an error.
plaintext = alices_box.decrypt(encrypted)
print(plaintext)
print(type(plaintext))
print(plaintext.decode('utf-8'))

import nacl.encoding
import nacl.signing

# Generate a new random private key for Bob (we call this a signing key)
bobs_private_key = nacl.signing.SigningKey.generate()
print(bobs_private_key)
print(type(bobs_private_key))

# Sign a message with it
signed = bobs_private_key.sign(b"Attack at Dawn")
print(signed)
print(type(signed))

# Obtain the verify key for a given signing key
bobs_public_key = bobs_private_key.verify_key
print(bobs_public_key)
print(type(bobs_public_key))

print(bobs_public_key.verify(signed))

# Serialize the verify key to send it to a third party
bobs_public_key_hex = bobs_public_key.encode(encoder=nacl.encoding.HexEncoder)
print(bobs_public_key_hex)
print(type(bobs_public_key_hex))
bobs_private_key = bobs_private_key.encode(encoder=nacl.encoding.HexEncoder)
print(bobs_private_key)
print(type(bobs_private_key))

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