Whether you’re a system administrator or a developer, protecting access to your remote servers is a priority.
The SSH (Secure Shell) protocol is designed to ensure a secure connection between two machines. But how exactly does this security process work?
Here’s a simple explanation of the various stages.
Establishing a secure connection
The first step is to create a TCP connection between the client and the SSH server. This secure tunnel ensures that all data exchanged is protected.
Negotiating versions and algorithms
Once the connection has been established, both parties negotiate the version of SSH to be used, as well as the cryptographic algorithms that will secure the communication. This step ensures compatibility and a high level of security.
Key generation and exchange
The client generates a key pair: a public key and a private key. It then sends the public key to the server. The server uses it to verify the client’s identity, using asymmetrical cryptography.
Session key calculation
On both sides, the client and server calculate a session key that will be used to encrypt all future communications. The server sends a random number encrypted with the client’s public key, which the client then decrypts using its private key.
Data exchange
As soon as the connection is established, all data sent between the client and the server is encrypted. This ensures that all information in transit is protected against interception or modification.
Credit: ByteByteGo
Secure transfer of orders and results
Commands sent by the client are first encrypted. The server then executes them and sends the encrypted results back to the client. This process ensures smooth, secure communication.
SSH’s three security layers
SSH relies on three distinct layers to guarantee the security of remote connections:
- Transport layer: Encrypts data to protect communication.
- Authentication layer: verifies client identity to ensure that only authorized users access the server.
- Connection layer: Allows multiple logical channels to be managed within the same connection.
Local SSH forwarding: a practical tool
Using a command like ssh -L p1:server:p2 remoteYou can create a secure tunnel through a firewall, allowing safe access to specific services.
SSH is a simple yet powerful tool for securing your remote connections. Whether you’re managing a server or transferring sensitive files, it provides reliable end-to-end protection.
If you’d like to receive support for your company’s cybersecurity needs, contact us today.
