Talking about the public and private key (theory)

　　I have always felt explain specialized knowledge of professional terms is a very serious matter but it is difficult to understand, so write this to understand the public and private key

Basic understanding:

　　1. must be paired public and private keys that each public key there is only a private key and a private key and each also has one and only one public key
　　2. The public and private keys are not as usual Like the key, only the decryption function, they have both encryption and decryption functions, but, something public key encryption, and only the corresponding private key can unlock, while the private key to encrypt something, and only phase the corresponding public key can unlock
　　3. in general, a pair of public and private key corresponding to the public key will be to get a lot of people, while the private key is generally only individuals (companies, organizations) holds

Let me give an chestnuts:

　　

In ancient times, there is John Doe two people, they are very good friends, and later Joe Smith to go out of business, before leaving, Joe Smith John Doe said: "I have a treasure, you told him to public key and the public key to use to tell a John Doe. " John Doe took it public 　　After years of Joe Smith really a fortune, think of the good friend John Doe, John Doe John Doe intend to go back and take some good things, but then, in ancient times, whether or communications traffic is very underdeveloped, most people are afraid things being transferred packet, but Joe Smith and are not afraid of his stuff was transferred packet, why? Because he has the private key ah 　　Joe Smith John Doe's going to put things, a list of the column, and the private key secret list of added, so that the handwriting on the list, it becomes something other people do not understand, then Joe Smith put the encrypted together with the list of the package to the Escort 　The first dart transportation: 　　personal bodyguard to see that piece of paper above all Stop being a hypocrite, Joe Smith thought it was a wrong, put the list to throw, but also feel personal bodyguard anyway, John Doe did not know what Joe Smith gave it secretly hiding some things, collect things, when the results of John Doe did not see the list goes on, it is rejected, the personal bodyguard also know that John Doe secretly hidden things, did not dare blow up, then return the same way, Zhang thirty-one did not see the share list, you know how it happens 　a second dart transportation: 　　personal bodyguard find something or so, but still goes Stop being a hypocrite, you know, maybe it was a keepsake, and then secretly hidden something, this time to see a list of John Doe, on the first list to get the house, secretly with the public key to decrypt, Joe Smith sent down what things are, and then to count the parcel and found lacking what, or reject, no way, wrong personal bodyguard, and went to 　third dart transportation: 　　personal bodyguard did not go back, I felt quite scary, to put things out, then went home to John Doe, John Doe inventory about it, feeling things together, and to accept it, and also wrote The letter, written after encrypted with the public, and let personal bodyguard sent back, a look at the personal bodyguard, but also Stop being a hypocrite, you know, all this trouble again Stop being a hypocrite, but no way, after all, send something, but also should consignee keepsake consignor, or personal bodyguard empty rumor it is to say sent Would not it be total chaos? 　　Joe Smith John Doe received a letter back to the room with the private key to decrypt, knowing what had happened, but since the Escort to put things, and that's paid for, as later accounts does not count, and that is what happened later

Follow-up and think:

　　

Although the example above, John Doe also encrypted with the public the letter to Joe Smith, but in fact, this is actually very safe, such as personal bodyguard to John Doe's public key stolen, then disguised John Doe and write encrypted with the public, so Joe Smith would be deceived into, so in most cases, are using private key encryption, public key and only used to verify, sent from the other side of things, is not what someone else has been modified of. 　　If the private key that was stolen out? I think this is not a problem we thought, but the major problem of the Internet companies to think, why would I say that the public key stolen it? Because the public was called public key, that is, give a lot of people, such as you download something, if you do not have your public key to verify how you download something it has not been hacked? 　　 　　以上，便是我对公钥私钥的见解，至于具体怎么加密解密，以及如果镖师自己造了一对公钥和私钥，并且把李四的公钥替换的时候该怎么办？这就是另外一个故事了

 　　

　　　　我一直觉得专业术语解释专业知识虽然严谨，但是很让人难以理解，不过我也知道有时候强行加入自己的理解，反而更容易让人误会，但还是写了这个，如果让您觉得困难，还请多多见谅