DHCP and SSH Services: Configuration, Security, and Encryption

Posted on Feb 10, 2025 in Contemporary Music Composition

DHCP Service Explained

Item 8. What is the DHCP service? Dynamic Host Configuration Protocol (DHCP) offers fast network configuration for clients. The administrator can assign dynamic IP addresses to clients through the DHCP server, without requiring manual configuration of IP, subnet mask, gateway, etc. The DHCP protocol uses UDP ports 67 and 68 for communication between server and client.

The DHCP server can automatically configure:

  • Client IP address
  • Subnet Mask
  • Lease time
  • Renewal time
  • Rebinding time

DHCP Client: A machine that requests the service provided by DHCP servers.

WINS: Windows Internet Name Service. It is a system that determines the IP address associated with a particular machine.

IP Address Allocation Methods

Regarding the allocation of IP addresses, the DHCP service has three options:

  1. Manual or static IP address assigned to a particular machine.
  2. Automatic assignment: assigns an IP address permanently to the first client machine making the request to the DHCP server until the client releases it.
  3. Dynamic allocation: assigns a client machine’s IP address temporarily (leases).

Advantages of Automatic or Dynamic Allocation

  • TCP/IP settings are assigned when you boot the client without any administrator intervention.
  • It centralizes information, reducing errors once configured and tested.
  • It saves time and effort of administration, increasing network security and preventing duplicate IP addresses or incorrect values.
  • It enables the movement of equipment between different subnets in a network.

Disadvantages of Manual Allocation

  • TCP/IP settings must be entered on each computer manually.
  • There is a possibility of mistakes and having to reconfigure TCP/IP.
  • More time is required to set those values, and any change in the network may cause more bugs.
  • You must change the IP manually each time a team relocates.

SSH Service Explained

Item 9. What is the SSH service? SSH (Secure Shell) is a tool that enables secure connections between computers connected by an insecure network. It uses port 22 and operates client-server. Its aim is to establish remote connections to allow secure transmission of any data type.

SSH Advantages

  • After the first connection, the client can verify that it is connecting to the same server in future sessions.
  • The client transmits the necessary information to the server for authentication (username and password) in encrypted format.
  • All data sent and received during the connection is encrypted.
  • The customer can run graphical applications from Shell safely (X11 forwarding).

Security Measures with SSH

With the use of SSH, the following are avoided:

  1. Interception of communication between two systems by a third machine that copies the information flowing between them, and can make amendments and forward to the target machine.
  2. Host spoofing or masquerading, i.e., a machine pretending to be the destination of a message machine.

Encryption: Types of Encryption

The encryption technique solves these kinds of problems:

  • Privacy and confidentiality: no one other than their legitimate recipient can access the information.
  • Integrity: the information cannot be altered (undetected change) in transit from sender to receiver.
  • Authentication: both the sender and the recipient can confirm the identity of the other party involved in the communication.
  • Non-repudiation: the creator or originator of the information cannot deny that they are the author.

The encryption types are:

  • Symmetric encryption or shared key.
  • Asymmetric encryption or public/private key.

Symmetric Encryption or Shared Key

It is based on using a key that both the sender and the receiver know.

Advantage: very efficient as the algorithms used are very fast.

Disadvantage: both parties must know the key.

DES Algorithm

The DES algorithm (Data Encryption Standard) and its main features are:

  • It was developed by IBM.
  • It is mainly used in banking.
  • It fell into disuse.

IDEA Algorithm

The IDEA algorithm (International Data Encryption Algorithm) and its main features are:

  • It was created in Europe.
  • It’s simple and fast programming.
  • It has never been broken at the moment.