LAB
1
Old srand() / rand()
• srand(1) + rand
• srand(time(NULL)) + rand
Other options:
• gettimeofday()
• clockgettime()
2
Linux
• /dev/random
• /dev/urandom
• Write function that will return random data from
/dev/random
- int getrdata (int number, unsigned char *buffer)
- read() can be interrupted (when handling signals etc.)
- take care of ‘short’ read
3
Linux
• check entropy available
– use system() func – previous LAB
• What is returned value of system() call?
• How to get
– print to file
– or use popen()
4
Windows CryptoAPI
• CryptAcquireContext()
- PROV_RSA_FULL – default provider
• CryptReleaseContext()
CryptGetRandom()
5