Encryption 🔒

Le encryptionencryption, also known as cryptography in common parlance although this term is inappropriate, is a technique which consists in transforming comprehensible data, called data in plain Englishin an illegible and incomprehensible format called figures with the help of mathematical algorithms and one or more encryption keys.

This transformation ensures that only people with the decryption key (or the corresponding keys in the case of two-key systems) can read and understand the original content.

The aim is to protect the confidentiality, l'integrity and sometimes theauthenticity information, preventing it from being consulted or modified by unauthorised persons.

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How it works

 

• Clear text → Original data (e.g. a message, a file).
• Encryption key → Secret value used by the algorithm to scramble the data.
• Encryption algorithm → Complex mathematical method (e.g. AES, RSA, SHA-256).
• Encrypted text → Result incomprehensible without the decryption key.

 

2 main phases:

• Encryption : an encryption algorithm is used with a data encryption key  to transform plain text into ciphertext.
• Decryption : To read the original message, the recipient uses a decryption algorithm and a decryption key

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Types of encryption

 

Symmetric encryption (secret key) 🔑

• A single key used to encrypt and decrypt.
• Examples AES (Advanced Encryption Standard), DES.
• Advantage Fast and efficient for large volumes of data.
• Disadvantage Risk if the key is compromised.

 

Asymmetric encryption (public key/private key) 🔑⬆️🔑⬇️

• Use a pair of keys a public (to calculate) and a private (to decipher).
• Examples RSA, ECC (Elliptic Curve Cryptography).
• Advantage Secures exchanges without private key sharing.
• Disadvantage Slower than symmetrical encryption.

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Applications

Encryption is ubiquitous in our digital lives and is used to secure a multitude of applications and data, including :

• Secure Internet communications (HTTPS): theSSL/TLS (often using a mix of symmetric and asymmetric encryption) ensures the confidentiality and integrity of data exchanged between your browser and websites (e.g. online banking 💳 , online shopping 🛒).
• Encrypted emails (PGP, S/MIME) 📧 : Protects the confidentiality of email content.
• Data storage : Hard drives, USB sticks, smartphones and cloud back-ups can be encrypted to protect data in the event of loss or theft.
• Virtual private networks (VPN) : Encryption is at the heart of VPNs for securing Internet connections and protecting online privacy.
• Encrypted instant messaging : Signal, WhatsApp... Ensure that only the sender and recipient can read messages.
• Authentication : Digital signature. Asymmetric encryption is used to verify the identity and integrity of digital documents.
• Cryptocurrencies Secure blockchain transactions (e.g. Bitcoin).

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Importance of encryption

In a world that is increasingly connected and dependent on digital data, encryption has become an essential tool. an essential component of information security and privacy protection. It allows you to :

• Protecting sensitive information against unauthorised access (espionage , data theft).
• Guaranteeing the confidentiality of communications.
• Ensuring data integrity (to prevent unauthorised modification of information).
• Building trust in digital systems and services.
• Meeting regulatory requirements in terms of data protection (such as the RGPD).

 

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⚠️ Limitations and challenges

• Key length A longer key (e.g. AES-256) increases security.
• Vulnerabilities attacks by brute force or algorithmic flaws (e.g. obsolete SHA-1).
• Key management Losing a key makes data permanently inaccessible.
• The rise of the cloud The spread of cloud services has increased the importance of encryption to protect data at rest and in transit.
• Key management challenges In cloud environments, the issue of key control (managed by the supplier or by the company) remains crucial to prevent unauthorised access in the event of compromise.
• The arrival of quantum computing It poses a long-term threat to current algorithms, prompting the development of new solutions. post-quantum cryptography. To find out more : Cybersecurity: dealing with the quantum threat
• Increased regulation standards such as NIS2REC and DORA require companies to have a high level of cyber security, on pain of financial and criminal penalties.
• Regulations restrictive some countries impose restrictions (e.g. ban on end-to-end encryption).
• Performance Encryption can slow down systems if it is poorly optimised.

 

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Most common key lengths

The strength of an encryption algorithm depends largely on the length of the key used. Here is an overview of the key lengths typically used for the most common algorithms:

For symmetrical algorithms (e.g. AES) :

• AES-128 Use a 128-bit. Offers a very good compromise between safety and speed.
• AES-192 Use a 192 bits. Slightly slower than AES-128, but with enhanced security.
• AES-256 Use a 256-bit. Preferred in environments requiring maximum protection (e.g. classified data, financial transactions).

For asymmetric algorithms :

RSA :

• RSA 1024 bits Once common, it is now considered insufficient (equivalent to around 80 bits of symmetrical security).
• RSA 2048 bits Current minimum standard, offering a security level of around 112 bits.
• RSA 3072 bits Approximately equivalent to 128 bits of symmetrical security.
• RSA 4096 bits Used when a very high level of security is required.
  

ECC (Elliptic Curve Cryptography) :

• 224-bit ECC 112-bit security.
• 256-bit ECC Very common, providing security equivalent to approximately 128-bit symmetrical encryption.
• 384-bit ECC Corresponds to approximately 192 bits of symmetrical security.
• 521-bit ECC Used for maximum security, equivalent to approximately 256 bits of symmetrical security.
  

Because of their efficiency, asymmetric algorithms such as ECC provide a high level of security while using much shorter keys than RSA, which reduces the computational load for encryption and decryption.