Shulou(Shulou.com)06/01 Report--

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.

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