Introduction
Differences between Clear Text, Cryptography Protocols & VPNs
Clear-text:
Easy to intercept, eavesdrop & mangle.
Use clear-text only on trusted networks.
Cryptographic Protocols:
Protocol encrypts information transmitted to protect the communication.
Prevents eavesdropping.
Need to transmit clear-text anyways? Wrap your communication into a tunnel.
Protocol for Tunneling = VPN.
VPN:
A VPN uses cryptography to extend a private network over a public one.
Protected connection a to a a private network.
A VPN connection is needed for using the course Labs.
HTTP(s) Traffic Sniffing with Wireshark
There are 2 websites using HTTP and HTTPS respectively, differences in the communication can be checked through a sniffer as Wireshark and using the command 'Follow TCP Stream':
Basic Binary and Hexadecimal Arithmetic
Binary
1 + 1 = 10
111 + 1 = 1000
1101b=13d
Converting Decimal and to Binary
Divide by 2 and keep a not of the remainder iterating the same operation until the dividend is zero.
13d is 1011b:
| Step | Operation | Remainder |
|---|---|---|
1 | 13 / 2 = 6 | 1 |
2 | 6 / 2 = 3 | 0 |
3 | 2 / 2 = 1 | 1 |
4 | 1 / 2 = 0 | 1 |
Binary Operators
| Name | Description | Example |
|---|---|---|
| Negation |
|
| if (both bits in the comparing position are ones) -> 1; else 0 |
|
| if (at least one of the bits is one) -> 1; else 0 |
|
| if (just one of the bits is one) -> 1; else 0 |
|
Hexadecimal
Hex | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F |
Dec | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
0x3a1 = 3a1h = 929d
| Conversion | Operation | Total |
|---|---|---|
3 = 3 | 3 * 16^2 | 768 |
a = 10 | 10 * 16^1 | 160 |
1 = 1 | 1 * 16^0 | 1 |
Converting decimal to hexadecimal
Similar to converting decimal to binary: 1019d = 0x3FB
| Number/16 | Result | Reminder * 16 |
|---|---|---|
1019 / 16 | 63.6875 | 0.6875 * 16 = 11 (B) |
63 / 16 | 3.9375 | 0.9375 * 16 = 15 (F) |
3 / 16 | 0.1875 | 0.1875 * 16 = 3 |
0 / 16 | -- |
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