Android security encryption: Message Digest

Android security encryption feature article index

All the above contents, such as symmetric encryption, asymmetric encryption, message digest and digital signature, are used as a preparatory knowledge to understand the working principle of digital certificate. Digital certificate is the ultimate weapon in cryptography and the crystallization of wisdom summarized by human history for thousands of years. Only after understanding the working principle of digital certificate can we understand the secure communication mechanism of HTTPS protocol. Finally, it can be handy in the SSL development process.

In addition, symmetric encryption and message digest can be used separately.

Knowledge points in series:

Digital certificate uses all the knowledge learned above

Through the study of the above contents, we should be able to master the following knowledge points:

1. Common algorithms

MD5, Sha, CRC, etc

2. Usage scenario

For example, the data fingerprint of the software download station: http://dev.MysqL.com/downloads/installer/

3. Use steps

The result of message summarization is fixed length. No matter how large your data is, even if it is only one byte or a G file, the result of message summarization is fixed length.

I often hear people ask such questions. How many are the results after MD5 summary? Some people say it's 16 bits, some say it's 128 bits, and some say it's 32 bits. How long is it? At this time, we should understand that 16 bits refer to the number of bytes, 128 bits refer to the number of bits, and 32 bits refer to the number of characters converted into hexadecimal display.

4. Principle of digital summarization