Encryption is the foundation of digital security — protecting everything from your online banking to confidential business files. But how does it actually work, and why does it matter so much for modern businesses?
What Is Encryption?
At its core, encryption is the process of transforming readable data (called plaintext) into an unreadable scrambled form (called ciphertext) using a mathematical algorithm and a key. Only someone with the correct key can reverse the process — called decryption — and read the original data.
Think of it like a padlock. Anyone can see the padlocked box, but only the person with the key can open it and access the contents inside. In digital terms, the “box” is your encrypted data and the “key” is a long string of mathematical values generated by an encryption algorithm.
The Two Main Types of Encryption
Symmetric Encryption
In symmetric encryption, the same key is used to both encrypt and decrypt the data. It’s fast and efficient, making it ideal for encrypting large amounts of data — like the contents of a hard drive or a large database.
The most widely used symmetric encryption standard today is AES (Advanced Encryption Standard), specifically AES-256. The “256” refers to the key length in bits — a 256-bit key has 2²⁵⁶ possible combinations, a number so astronomically large that brute-force cracking is computationally infeasible with any technology that exists or is foreseeable. AES-256 is used in BitLocker, HTTPS, VPNs, and most modern security systems.
The challenge with symmetric encryption is key exchange: how do you securely share the key with the other party without it being intercepted? This is where asymmetric encryption comes in.
Asymmetric Encryption (Public-Key Cryptography)
Asymmetric encryption uses a mathematically linked key pair: a public key that anyone can have, and a private key that only you hold. Data encrypted with your public key can only be decrypted with your corresponding private key — and vice versa.
This solves the key exchange problem elegantly. If Alice wants to send Bob an encrypted message, she encrypts it with Bob’s public key (which Bob has published openly). Only Bob’s private key — which Bob keeps secret — can decrypt it. Even Alice cannot decrypt the message once she’s sent it.
Asymmetric encryption is the basis of:
- HTTPS — securing websites and web applications
- Email encryption (S/MIME, PGP)
- Digital signatures — proving the authenticity and integrity of files and communications
- TLS handshakes — the process by which secure connections are established between clients and servers
The most widely used asymmetric algorithms are RSA and Elliptic Curve Cryptography (ECC), the latter being more efficient for equivalent security strength.
How HTTPS Works: A Practical Example
When you visit a website using HTTPS (the padlock in your browser bar), a process called a TLS handshake takes place in milliseconds:
- Your browser requests a secure connection and the server presents its digital certificate — an asymmetric public key verified by a trusted Certificate Authority
- Your browser and the server use asymmetric encryption to securely agree on a temporary session key
- For the rest of the session, all data is encrypted using fast symmetric encryption (AES) with that session key
- Even if someone intercepts every packet of data, they see only encrypted ciphertext — the session key is never transmitted unencrypted
This hybrid approach — asymmetric for key exchange, symmetric for bulk data — is how virtually all secure internet communication works.
Hashing: Encryption’s Close Relative
Often discussed alongside encryption is hashing — a one-way mathematical function that converts data of any size into a fixed-length fingerprint (called a hash or digest). Unlike encryption, hashing cannot be reversed. The same input always produces the same hash, but you cannot derive the input from the hash alone.
Hashing is used to:
- Store passwords securely — systems store the hash of a password, not the password itself. When you log in, your input is hashed and compared to the stored hash
- Verify file integrity — software downloads often include a hash so you can confirm the file hasn’t been tampered with in transit
- Digital signatures — a document is hashed, and the hash is encrypted with the sender’s private key, creating a verifiable signature
Modern secure hashing algorithms include SHA-256 and SHA-3. MD5 and SHA-1 are considered broken for security purposes and should not be used.
Why Encryption Matters for UK Businesses
Protecting Data at Rest
Data at rest — files on laptops, servers, USB drives, and backup media — needs encryption to be protected if the physical device falls into the wrong hands. Without encryption, anyone with physical access to a drive can read its contents. With encryption (such as BitLocker for Windows or FileVault for macOS), the data is unreadable without the correct key.
Protecting Data in Transit
Data in transit — emails, file transfers, API calls, remote desktop sessions — is vulnerable to interception. Encryption protocols like TLS, SFTP, and VPNs protect data as it moves across networks. Unencrypted protocols (plain HTTP, FTP, Telnet) should be disabled entirely in business environments.
UK GDPR and Regulatory Compliance
Under the UK GDPR, encryption is explicitly cited in Article 32 as an example of an appropriate technical measure to protect personal data. The ICO considers encryption a baseline expectation for personal data stored on portable devices, transmitted electronically, or processed in cloud environments. Data breaches involving unencrypted data are treated more seriously by the regulator than those involving properly encrypted data.
The Quantum Computing Caveat
Looking further ahead, quantum computing poses a theoretical future threat to current asymmetric encryption algorithms (RSA and ECC). Post-quantum cryptography standards are being developed by NIST and others. For most businesses this is a future consideration rather than an immediate concern — but organisations handling long-term sensitive data (government, defence, healthcare) should monitor the space and the timeline for quantum-resistant algorithm adoption.
How BIT Tech Can Help
From deploying BitLocker on your Windows fleet to ensuring all business web traffic uses HTTPS, configuring encrypted VPN access for remote workers, and advising on email encryption — BIT Tech IT Solutions helps businesses implement encryption correctly across their IT estate.
If you’d like to review how encryption is applied in your organisation, contact our team for a consultation.
