Cryptography and identity Authentication Technology-- principles and practical applications of PKI & lt;1>
Encryption and decryption authentication
1. Symmetrical encryption
Single key encryption:
Advantages: 1. Encryption is faster than asymmetric key 2. A large number of digits is difficult to break.
Disadvantages: 1. A security mechanism is needed to distribute keys 2. It is difficult to manage the key. Symmetric encryption provides confidentiality but cannot
Provide authentication and non-repudiation.
Algorithm: DES,IDEA,RC2,RC4,RC5,AES,SKIPJACK
two。 Asymmetric encryption:
Private key | | public key
Note: keys are used in pairs when using asymmetric key algorithms. Public key encryption, private key decryption. The guarantee of confidentiality.
Digital signature:
Identity authentication function: 1.A uses A's private key to encrypt information 2.A transmits encrypted information to B. The confidentiality of information cannot be guaranteed.
Advantages: 1. There is a better key distribution function 2. More scalable. 3. Provide source authentication and non-repudiation functions.
Disadvantages: 1. Slow. two。 The mathematical model is complex.
Algorithm: RSA,Ecc,Differ-Hellman,ELGamal,DSA.
3. Stream passwords and block ciphers:
Symmetric cipher algorithm: block cipher and stream cipher.
Block cipher: acts on ciphertext combination plaintext groups. Group first and then encrypt by group.
Stream cipher: acts on plaintext stream and ciphertext stream, encrypting one bit at a time. Mathematical functions act on every bit. We need more.
Processing ability, suitable for hardware platform.
IV initializes the vector value. Improve randomness.
4. Mixed encryption (widely used):
1. Symmetric key encrypts huge amounts of data. two。 Asymmetric key (public key) encrypts a symmetric key.
two。 Use the private key to decrypt the symmetric key. 3. The public key decrypts document information.
The symmetric key is obtained by algorithm. Differ-Hellman
Message integrity in digital authentication
1. One-way hash function:
It does not use any function itself, which can convert a longer string or message into a fixed-length value.
Hash algorithm-- > data message-- > message digest-- > send-- > Hash algorithm-- > message digest compares the message digest sent into
OK, check.
Note: there is no security for simple hash functions.
two。 About HMAC and CBC-MAC
HMAC: a hash with an authentication code message.
Message + symmetric key-- "Hash algorithm--" MAC value-- "message + symmetric key--" Hash algorithm-- "MAC value comparison
The MAC value sent.
CBC-MAC: use symmetric block ciphers to encrypt data in CBC mode, and output plaintext for MAC calculation.
Note: do not use the same key to complete block encryption and authentication.
3. Various hash algorithms:
Message digest algorithm 2 (MD2) 128bit hash
Message digest algorithm 4 (MD4) 128bit hash
The 128bit hash of message digest algorithm 5 (MD5) is more complex than that of MD5.
Modification of MD5 by HAVAL algorithm
The secure hash algorithm produces a hash value of 160bit and is applied to DSA.
SHA-I/Hash-256-sha-384/sha-512 sha-1:160/256 256
3. Digital signature:
Function: to prevent data from being tampered with or denied during transmission.
A Mui-"data message--" get the hash a by hashing-- "encrypt the private key of a to the hash value of a Mui -" get the data message a Mui-"the public of a
The key decryption hash value a muri-"gets the data message a compared with the local hash operation result.
Note: digital signatures do not guarantee confidentiality
Functions: integrity, source authentication, non-repudiation protection, use of asymmetric keys but no confidentiality.
4. Standards for digital signatures:
The secure hash algorithm is to ensure the integrity of the message, and the digital signature is to digitize the secure hash.
Algorithm: RSA,DSA can only be used for digital signature.
5. Various biological identification techniques
Iris, fingerprints, facial recognition.
Fingerprint evaluation machine, notebook face recognition, retina recognition technology.
