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Definition: Cryptography is the practice and study of secure communication techniques that allow only the sender and intended recipient of a message to view its contents. It involves creating written or generated codes that disguise the meaning of a message to protect information from being accessed by unauthorised parties.

Cryptography is essential for protecting sensitive data both in storage and during transmission. It underpins various security measures including encryption, hashing, and digital signatures. Encryption transforms readable data, or plaintext, into an encoded version called ciphertext, which can only be decrypted by authorised parties possessing the correct decryption key. Hashing converts data into a fixed-size hash value or digest, which uniquely represents the original data. Digital signatures provide a means to verify the authenticity and integrity of electronic documents and messages.

The effectiveness of cryptographic techniques depends on factors such as the encryption algorithm’s strength, the keys’ length and security, and the randomness of key generation. Cryptography is dynamic, constantly evolving to address emerging threats and exploit new technologies.

What is symmetric and asymmetric cryptography?

Symmetric cryptography requires only a singular key to encrypt and decrypt a message. Asymmetric cryptography, or public key cryptography, instead uses two different keys to encrypt and decrypt data: the public key and the private key. The public key encrypts the selected message, whereas the private key decrypts it.

What is the purpose of post-quantum cryptography?

Postquantum cryptography aims to develop new cryptographic algorithms that are secure against attacks by quantum computers. The algorithms created rely on different mathematical problems that are hard to solve not only for us but also for quantum computers. As post-quantum cryptography is considerably more efficient than classical cryptography, organisations like governments and financial institutions are investing in it to guarantee that their data and communications will be secure from quantum computing attacks.

What are the applications of cryptography?

As technology develops, cryptography is becoming increasingly important in many fields. One of those fields is digital currency. Cryptography can be seen in the blockchain technology used in cryptocurrencies, as each transaction on the blockchain is encrypted, and only users can access their data by using their private keys. Cryptography makes tampering with data difficult, keeping people’s information secure.

Cryptography is also applied to e-commerce. Online transactions are encrypted so that third parties and threat actors cannot understand the data. E-commerce site passwords are also protected by keys to ensure that no hacker can access our details. 

Key Characteristics:

  • Secure Communication: Ensures that messages can be read only by the sender and intended recipients.
  • Encryption and Decryption: Protects data by making it unreadable without the correct key or cipher.
  • Integrity and Authenticity: Hash functions and digital signatures verify that data has not been tampered with and confirm the identity of the sender.
  • Constant Evolution: Cryptographic methods and algorithms are continually being developed and refined in response to evolving security requirements and computational capabilities.


  • Real-World Example: SSL/TLS encryption is used to secure internet communications, such as online banking transactions and email correspondence.
  • Hypothetical Scenario: A classified government document is encrypted using a strong cryptographic algorithm to protect its contents from being compromised if intercepted.

Related Terms:

  • Encryption: The method by which plaintext is converted to ciphertext to prevent unauthorised access.
  • Hashing: A process of converting data into a fixed-size string of characters, representing the data uniquely.
  • Digital Signature: An electronic form of a signature that ensures the integrity of a document or message and its sender.

What is the OWASP Top 10: Download our flash cards to find out.

Inside you will find a description of the most common web vulnerabilities.

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