What is Encryption?

Encryption is the process of converting readable data (plaintext) into an unreadable, scrambled form (ciphertext) using a mathematical algorithm and a key, so that only someone with the correct key can convert it back and read it.

Encryption protects data by scrambling it into ciphertext that is meaningless without the right key. An algorithm and a key transform readable plaintext into ciphertext; the correct key reverses the process. This keeps data confidential whether it is stored on a disk or moving across a network. Encryption underpins secure websites, online banking, messaging, and virtually all modern digital security.

Key Takeaways

• Encryption converts readable plaintext into scrambled ciphertext using an algorithm and a key, so only someone with the correct key can read it.
• It protects both data at rest (stored files, disks, databases) and data in transit (network traffic, web browsing, messaging).
• There are two main types: symmetric encryption (one shared key, fast, for bulk data) and asymmetric encryption (a public and private key pair, for secure key exchange and digital signatures).
• Beyond confidentiality, encryption supports integrity (detecting tampering), authentication (verifying identity), and non-repudiation (proving who sent something).
• Encryption is required by regulations such as GDPR, HIPAA, and PCI DSS, and is moving toward post-quantum algorithms as quantum computing advances.

How Encryption Works

Encryption uses an algorithm and a key to transform data. The algorithm is the mathematical procedure that scrambles the data; the key is the secret value that controls how the scrambling happens. The same algorithm with a different key produces different ciphertext, so the security depends on keeping the key secret, not on hiding the algorithm.

The process is straightforward in principle. Plaintext (the readable data) goes into the encryption algorithm along with a key, and ciphertext (the scrambled data) comes out. To reverse it, the ciphertext goes into the decryption process with the correct key, and the original plaintext is recovered. Without the key, the ciphertext is meaningless. It is like a locked box: anyone can see the box, but only the person with the key can open it and read what is inside.

What Encryption Protects: The Four Goals

Encryption and related cryptographic techniques support four core security goals.

• Confidentiality: Keeping data secret from anyone without the key. This is the primary purpose of encryption.
• Integrity: Detecting whether data has been altered. If ciphertext or its authentication tag is tampered with, decryption fails or the change is detected.
• Authentication: Verifying the identity of the sender or the source of the data, often through digital signatures and certificates.
• Non-repudiation: Preventing a sender from denying they sent a message, achieved through digital signatures backed by asymmetric cryptography.

Data at Rest and Data in Transit

Encryption protects data in two fundamental states, and most organizations need both.

• Data at rest: Information stored somewhere: files on a disk, records in a database, backups in the cloud. Disk encryption tools such as BitLocker and server-side cloud encryption protect data at rest, so a stolen drive or breached storage bucket reveals only ciphertext.
• Data in transit: Information moving across a network: a web request, an email, a VPN session. Protocols such as TLS (which secures HTTPS websites) and VPNs encrypt data in transit, so intercepted traffic cannot be read.

A complete security posture encrypts data in both states, because data is vulnerable both when stored and when moving.

The Two Main Types of Encryption

Encryption algorithms fall into two families, distinguished by how they handle keys. Most real systems use both together.

Attribute	Symmetric Encryption	Asymmetric Encryption
Keys	One shared secret key for both encryption and decryption	A public key to encrypt and a private key to decrypt
Speed	Fast; efficient for large data	Slower; computationally heavier
Main use	Bulk data, disk encryption, VPN and TLS data channel	Secure key exchange, digital signatures, secure email
Key challenge	Distributing the shared key securely	Slower performance; larger keys
Example algorithms	AES, Twofish	RSA, ECC (elliptic-curve cryptography)

For a deeper look at each, see EC’s explainers on symmetric encryption and symmetric vs asymmetric encryption. In practice the two are combined into a hybrid system: asymmetric encryption securely exchanges a symmetric session key, and fast symmetric encryption then protects the actual data. This is how TLS secures websites.

Common Applications of Encryption

• Secure communication: Messaging apps, email, and voice calls use encryption to protect content from interception.
• Web browsing (HTTPS): TLS encrypts the connection between your browser and websites, protecting logins, payments, and form data.
• Data storage: Cloud services and devices encrypt stored files so they stay confidential even if the storage is breached.
• Online transactions: E-commerce and banking encrypt financial data during payments.
• Passwords and authentication: Sensitive credentials are protected using cryptographic techniques so they cannot be easily stolen.

Encryption and Compliance

Encryption is not just good practice; it is often a regulatory requirement. Standards and laws including GDPR, HIPAA, PCI DSS, FIPS, and CCPA require organizations to protect personal, financial, and health data, and encryption is a primary control for meeting those obligations. Properly encrypted data is also frequently treated more favorably under breach-notification rules, because exposed ciphertext is not usable without the key.

Challenges of Encryption

Encryption is powerful, but implementing it well involves real trade-offs.

• Key management: The hardest part of encryption is not scrambling data but managing keys: generating, distributing, storing, rotating, and destroying them securely. Poor key management, not weak algorithms, is the usual point of failure. Hardware security modules (HSMs) are used to protect keys.
• Data discovery: Organizations must first find the sensitive data that needs encrypting across structured and unstructured stores, which is a significant task in itself.
• Performance overhead: Encryption and decryption consume compute resources, so algorithm and key-size choices must balance security against performance.
• Searching encrypted data: Querying data while it stays encrypted is difficult, and repeated decryption to search can increase exposure.
• The backdoor debate: Governments periodically seek lawful access to encrypted data, raising an ongoing tension between privacy, security, and law enforcement.

Encryption and the Post-Quantum Future

Encryption is entering a major transition. A sufficiently powerful quantum computer running Shor’s algorithm could break the asymmetric encryption (RSA and elliptic-curve cryptography) that protects key exchange and digital signatures today. To prepare, NIST standardized post-quantum algorithms in August 2024, including ML-KEM (FIPS 203) for key establishment and ML-DSA (FIPS 204) for signatures.

Symmetric encryption is far less affected: AES-256 remains secure. Organizations are beginning to migrate, and EC’s post-quantum cryptography resources cover how to plan that transition.

How Encryption Consulting Helps

Encryption is easy to turn on and hard to get right, because the difficulty lies in choosing the right algorithms, managing keys securely, and meeting compliance obligations across a whole organization. Encryption Consulting’s Encryption Advisory Services provide assessment, strategy, and implementation planning: identifying sensitive data, designing an encryption architecture aligned to NIST and FIPS guidance, and putting sound key management in place, including HSM-backed storage.

The goal is encryption that genuinely protects data and stands up to audit. Backed by ISO/IEC 27001:2022 and SOC 2 certified practices.

Frequently Asked Questions

What is encryption in simple terms?

Encryption is a way of scrambling readable information into an unreadable form so that only someone with the right key can unscramble and read it. It works like a locked box: you put your data in, lock it with a key, and only a person with the matching key can open it. This keeps your data private whether it is stored on a device or sent across the internet, which is why it protects things like online banking and messaging.

What is the difference between encryption and decryption?

Encryption is the process of converting readable plaintext into scrambled, unreadable ciphertext using an algorithm and a key. Decryption is the reverse process: converting the ciphertext back into the original plaintext using the correct key. They are two halves of the same system. Encryption protects the data, and decryption makes it readable again for the authorized person who holds the key.

What are the two main types of encryption?

The two main types are symmetric and asymmetric encryption. Symmetric encryption uses a single shared key for both encryption and decryption, and it is fast, making it ideal for large amounts of data. Asymmetric encryption uses a pair of keys, a public key and a private key, and it solves the problem of securely sharing a key. Most systems combine both: asymmetric encryption exchanges a key, and symmetric encryption protects the data.

What is the difference between data at rest and data in transit?

Data at rest is information that is stored somewhere, such as files on a hard drive, records in a database, or backups in the cloud. Data in transit is information moving across a network, such as a web request or an email. Encryption protects both: disk and storage encryption protect data at rest, while protocols like TLS and VPNs protect data in transit. A strong security posture encrypts data in both states.

Why is encryption important?

Encryption is important because it keeps sensitive data confidential even if it is intercepted or stolen. It protects personal information, financial transactions, health records, and private communications from unauthorized access. Beyond confidentiality, it also verifies that data has not been tampered with and confirms who sent it. Encryption is also required by regulations such as GDPR, HIPAA, and PCI DSS, making it both a security necessity and a compliance obligation.

Can encryption be broken by quantum computers?

Quantum computers threaten some encryption but not all. A powerful quantum computer running Shor’s algorithm could break the asymmetric encryption (RSA and elliptic-curve cryptography) used for key exchange and digital signatures. Symmetric encryption is far more resistant: AES-256 remains secure. To prepare, NIST standardized post-quantum algorithms in August 2024, such as ML-KEM and ML-DSA, and organizations are beginning to migrate their asymmetric cryptography to these quantum-resistant standards.

Strengthen Your Encryption Strategy

Turning encryption on is simple; using it well across an organization is not. Explore Encryption Consulting’s Encryption Advisory Services to assess your current encryption, design a strategy aligned to NIST and FIPS guidance, and put sound key management in place.