Assignment for week 8: The goal is to study and use OpenSSL API on two tasks -
generate an RSA key pair and use I/O (BIO) abstraction..

Deadline: November 10, 2021 (8:00 AM), maximum is 5+5 points.

Write two programs using OpenSSL library on Linux.

1) Create a program that generates 4096 bit RSA key
with public exponent 65537 and print private and public output
to the screen (in any form you want, but PEM is preferred).

Hints:
 - Use RSA_generate_key_ex() function.

 - Use PEM_read/write_PrivateKey or BIO based PEM_read/write_bio_PrivateKey
   (the same for public key).

 - Use OpenSSL documentation and man pages for functions description.

2) Create a program that decodes string below from base64 encoding, then
decrypts it and prints the plaintext to the standard output.

The ciphertext is base64 encoded, encrypted by AES-128 cipher in CBC mode
with padding. The ciphertext is defined by this C array:

const char *ENC =
"d21y+1uAWqh5juGqJL2snNINI58SV3PTpZWaM4cC6QfJMyndZ7HQS5yl5Zy36RXk\n"
"C5rsqlOdWXT8neXXcE8+U+l7I17j7Ytn/9p3UFHT1raYlZFAWgvXNyqymU2NlMWm\n"
"cjMmKqqxJ7pWHzFzKGdrTABxRFTuzWg3yWKK+dd7XtQnW2CUxlorF7qPG5vj1WEX\n"
"bDfBc4u02hRyS04okGBqsSYpn2BmOJ8XbeKaPmTu1pSytouJuMB5LrVdT9evklDY\n"
"3SH+tCcM26aCduGVHwakTnB6sU61JeIL/d8kC68nZsYoL6u4LZppCJSVnGgQgSNs\n"
"TVUXaJfauOTjjbvPFPm1x+NJJy7hVXjHX/kElwNXCmE=";

The KEY is "\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff"
and  IV is "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0f"
(in C string notation).

Hints:
 - KEY and IV is the same as in the previous assignment.

 - You should use BIO abstraction, notably BIO_f_cipher() and BIO_f_base64()
   pushed to the BIO stack and then use BIO_read().

 - The plaintext is ASCIIart image, so you can print it directly to terminal.


Your submitted archive should contain *two* C programs above and Makefiles.

The source code must be compilable on the provided virtual machine or on aisa server.