Cryptographic decryption and OpenSSL establishing a private CA

1. The establishment of an encrypted communication process:
   1. Sender:
      1. Extracts the signature of the data using a one-way encryption algorithm; "One-Way encryption algorithm"

         One-way encryption > signature + signature

      2. using your own Private key encryption signature, appended to the data, "Public key cryptography (non-heap encrypted)"

         public key cryptography >[signature redaction + data]

      3. generates a temporary key for symmetric encryption, Use this temporary key to encrypt the data and encrypt the data signature. "Symmetric encryption"

         symmetric encryption >[Ciphertext [signature ciphertext + data]]

      4. encrypts the temporary key with the recipient's public key, appended to the data behind the symmetric encryption.

         public key encryption (opponent) >[temporary key [ciphertext [signature ciphertext + data]]

   2. Receiver:
      1. decrypts the encrypted temporary key with its own private key;

         packet original: [Temporary key] [ciphertext [signature ciphertext + data]]

         public key cryptography >[ciphertext [signature ciphertext + data]] è temporary key

      2. uses temporary key to decrypt data and signature ciphertext,

      3. decrypts the signature cipher with the sender's public key to obtain the data's signature

         public key Cryptography > signature + data

      The
      4. uses the same one-way encryption algorithm as the other party to settle the signature of the data and compare it with the decrypted signature to verify the integrity and privacy of the data.

         One-way encryption > data integrity check

In the above encrypted communication process, the entire process is secure and encrypted, only when the public key encryption, can not verify that the resulting public key is the key of the subject or other people forged key, so need to do digital authentication:

1. encryption protocol and encryption algorithm:
   1. symmetric encryption:
      1. attribute:
         1. encrypted decryption using the same key
         2. separates plaintext into fixed large A small block, encrypted one after the other;
         3. its security relies on keys rather than algorithms (most algorithms are public)
      2. Common algorithms:
         1. Des:data Encryption Standard, 56bits
         2. 3DES
         3. aes:advanced encrpytion, (128bits,192,256,384,51 2bits)
         4. BlowFish
         5. twofish
         6. idea
         7. RC6
         8. cast5
      3. defect:
         1. too many keys;
         2. Key Distribution process potential risks.
   2. One-way encryption:
   3. Public Key cryptography:
      1. Features:
         key in pairs appears;

         ② public key is extracted from the private key,

         1. data encrypted with public key, Only private keys that are paired with this public key can be decrypted, and vice versa

         ④ key lengths, such as 512bits,1024,2048,4096bits

         ⑤ Commonly used for data signing and key exchange

Third, the authentication mechanism:

Cryptographic decryption and OpenSSL establishing a private CA