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Encryption and Decryption Techniques: Methods and Use Cases

Encryption scrambles readable data into ciphertext with a key. Decryption reverses it with the matching key. Almost every technique falls into one of three families: symmetric (one shared key), asymmetric (a public and private key pair) or hybrid (both together). The technique matters less than how you handle the keys. Most real-world failures come from keys that are stored badly, shared carelessly or never rotated. If you want the key handling taken off your hands, a password manager with encrypted storage, such as LogMeOnce, is built for exactly that job.

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TL;DR

Encryption is a reversible transformation of plaintext into ciphertext using a key. Decryption is the same process run backward with the right key.
Symmetric encryption (for example AES) is fast and suits large amounts of data. Asymmetric encryption (for example RSA or ECC) solves key sharing but is slower, so it mostly protects small payloads and key exchange.
Real systems are hybrid: asymmetric methods agree on a key, and a symmetric cipher then does the heavy lifting.
Hashing is not encryption. It is one-way, so it verifies data but cannot give it back.
Strong algorithms are useless with weak key management: generate, store, rotate and destroy keys on purpose.

What encryption and decryption actually do

NIST, the US standards agency, describes encryption as a reversible mathematical transformation that turns plaintext (readable data) into ciphertext (a random-looking string) using a cryptographic key. Decryption uses the corresponding key to turn the ciphertext back into the original.

Three parts are always present:

Plaintext: the message, file or password you want to protect.
Algorithm (cipher): the published mathematical procedure that does the scrambling.
Key: the secret value that controls the procedure.

The algorithm is usually public on purpose. The Open University explains that a secure cryptosystem should make it computationally infeasible to work out the plaintext from the ciphertext without the decryption key, even when everyone knows the algorithm. In other words, the secret lives in the key, not in the method. That is why this article spends as much time on keys as on ciphers.

Encryption shows up in more places than most people realize. Apple’s developer documentation lists certificates, digital signatures, secure keychain storage and secure transport of information among its use cases. The padlock in your browser, your saved passwords and your encrypted cloud folder all rely on the same ideas.

The main encryption techniques

The International Organization for Standardization (ISO) groups cryptography into symmetric-key and asymmetric-key systems, key management and hash functions. Here is what each means in practice.

Symmetric encryption: one key for both directions

In symmetric encryption the same key locks and unlocks the data. It is fast and efficient, which makes it the standard choice for encrypting files, disks, databases and the bulk of network traffic.

The catch is distribution. If you and a colleague both need the key, you must get it to them without anyone else seeing it. Every extra person or device that holds the key is one more place it can leak.

Symmetric ciphers come in two designs, as the OWASP Developer Guide explains:

Block ciphers process data in fixed-size blocks. AES is the best-known example.
Stream ciphers process a continuous stream of data. Salsa20 is an example.

For block ciphers, the mode of operation matters as much as the cipher. NIST materials list AES modes including ECB, CBC, CFB, OFB, XTS-AES, CCM and GCM. Modes differ in how they chain blocks together. Some, such as GCM and CCM, also check that the data was not altered. We cover this in more depth in our guide to AES-GCM encryption.

Asymmetric encryption: a public key and a private key

Asymmetric (public-key) encryption uses two mathematically related keys. Apple’s documentation notes that the public key may be distributed openly while the private key remains secret. Anyone can encrypt a message to you with your public key, but only your private key can decrypt it.

This removes the key-sharing problem. It also supports authentication: a message signed with your private key can be checked by anyone holding your public key. The Electronic Frontier Foundation’s guide points out the trade-off: asymmetric methods are substantially slower, so they fit small payloads and key establishment better than bulk data.

Common asymmetric algorithms are RSA and elliptic-curve cryptography (ECC). ISO notes that ECC can offer smaller, faster and more efficient keys. For a deeper walkthrough, see our page on asymmetric key encryption.

There is one more risk to understand. If an attacker swaps in their own public key, you would encrypt to the wrong person. The EFF explains that key fingerprints and website security certificates exist to let you verify whose key you are holding.

Hybrid encryption: how the internet actually works

Most secure connections combine the two. The slow asymmetric step is used briefly to agree on or deliver a fresh symmetric key. Then the fast symmetric cipher encrypts everything that follows. You get the convenience of public keys and the speed of shared keys.

This answers a question people often ask: which is faster, AES or RSA? AES, by a wide margin. They are not rivals, though. They do different jobs in the same system.

Comparing the common algorithms

Technique	Type	Keys	Typical use	Main trade-off
AES	Symmetric block cipher	One shared key	Files, disks, databases, network traffic	Key must be shared and protected
DES	Symmetric block cipher	One shared key	Legacy systems	Obsolete; migrate to current algorithms
Stream ciphers (e.g., Salsa20)	Symmetric stream cipher	One shared key	Continuous data streams	Same key-sharing issue as other symmetric ciphers
RSA	Asymmetric	Public and private pair	Key exchange, digital signatures	Slower; larger keys
ECC	Asymmetric	Public and private pair	Key exchange, signatures, constrained devices	Newer and less universally familiar than RSA
Hash functions	One-way	None	Integrity checks, signatures, checksums	Cannot be reversed

ISO names DES and AES as symmetric examples and RSA and ECC as asymmetric examples. NIST adds that AES is widely supported in current systems and software, and that AES-192 gives stronger protection than AES-128 because it has more possible key values. The same NIST publication recommends moving data protected by obsolete algorithms to current NIST-approved ones. If you still depend on an old cipher, treat migration as a project with an owner and a date.

Stronger is not automatically better in every setting. Apple’s documentation observes that more complex encryption can take longer and require keys too large to store easily, so strength has to be balanced against usability. For a ranked comparison, read our overview of the best encryption algorithms, and for a broader tour of families see different types of encryption.

Encryption, hashing and encoding are not the same thing

These three get confused constantly, and the mix-up causes real security mistakes.

Encryption is reversible with the right key. Use it when you need the original data back.
Hashing maps input of any length to a fixed-length digest and is designed to be one-way. ISO lists digital signatures, message authentication codes and checksums among its applications. Use it to verify that something has not changed, or to check a value without storing it in readable form.
Encoding (such as Base64) only changes the format of data so systems can handle it. It uses no secret, so it protects nothing.

The practical rule: if you must be able to recover the data, encrypt it. If you only need to confirm it matches, hash it. Never treat encoding as protection.

Key management: where encryption succeeds or fails

ISO is blunt on this point: weak key management weakens the protection of encrypted data, and it describes a lifecycle of generation, exchange or distribution, storage, use, safe destruction and replacement. The OWASP Key Management Cheat Sheet turns that lifecycle into concrete practice:

Generate keys in a compliant cryptographic module, using its random-bit generator. Keys you invent by hand, or derive from a memorable phrase alone, are predictable.
Transport keys over secure channels when they must move.
Use each key for one purpose. A key that encrypts data should not also sign documents.
Store keys in a protected cryptographic vault, never in source code, shared documents or chat messages.
Back up keys when recovery is required. A lost key means permanently unreadable data.
Set a risk-based cryptoperiod and rotate keys on that schedule.
Destroy secret and private-key copies when they are no longer needed.
Document the lifecycle, including what happens after a compromise.

The older US standard for financial institutions, FIPS 171, reached the same conclusions decades ago. It calls for keys to be randomly generated, and distributed, stored and destroyed or archived in a secure, controlled and auditable way. It also asks for tamper-resistant storage, dual control and accountability. These ideas still describe a sound key program.

A worked example

Imagine a 40-person company that encrypts customer files with AES. The cipher is fine. But the key sits in a shared spreadsheet, six former employees still have access, and it has never changed. Anyone with that spreadsheet can decrypt everything, so the encryption adds little. Fixing it means generating a new key properly, storing it in a vault with access limited to named people, rotating it on a schedule, and destroying old copies. None of those steps involves a better algorithm.

Which technique fits which reader

Individuals and families. You do not need to choose ciphers. You need your passwords, documents and cloud files encrypted by tools that handle keys for you, and a strong master password that only you know. Pair that with monitoring so you hear about exposed credentials early.

Small and medium businesses. Your biggest risk is key and credential sprawl: shared logins, shared keys, departing staff. Centralize secrets, give each person their own access, and remove it when they leave.

Large enterprises. Scale brings more systems, more keys and audit requirements. A documented key lifecycle, role-based access and a plan to retire obsolete algorithms matter most. Our overview of key encryption methods for enterprise data protection goes further.

Government agencies. Rely on NIST-approved algorithms and the documented practices in the sources above, and keep key handling auditable.

Managed service providers. You hold secrets for many clients. Separate each client’s keys and credentials, and make sure every technician’s access can be traced and revoked.

For developers choosing ciphers in code, our guide to encryption algorithms for developers explains why authenticated modes beat legacy ciphers.

Putting encryption to work with LogMeOnce

Understanding the techniques is the easy part. Running them every day, across passwords, files and teams, is where people slip. LogMeOnce offers a password manager, cloud storage encryption and passwordless multi-factor authentication so that protection does not depend on remembering anything.

For individuals, the published plans are Premium at $0 per month, Professional at $2.50 per month, Ultimate at $3.25 per month and Family at $4.99 per month. Dark Web Monitoring is $1.67 per month. For organizations, Teams is $4.00 per month per user and Business is $7.99 per month per user, with Enterprise available on request. Compare them on the pricing page or the business pricing page.

Our perspective

Every week people ask us which cipher is best. It is a fair question, but it is rarely the one that decides whether their data stays private.

The mainstream algorithms are well understood and widely available. What differs from one person or company to the next is the human layer: where the key lives, who can reach it, and whether anyone remembers to rotate it. That is why we build around the full picture: a password manager, encrypted cloud storage, passwordless multi-factor authentication and dark web monitoring working together.

Our view is simple. Strong encryption should be the default, not a project. When the tool handles the routine work, people actually use it, and that is when the math protects them.

Mike

FAQ

What is the difference between encryption and decryption?

Encryption converts readable plaintext into unreadable ciphertext using a key. Decryption converts the ciphertext back into plaintext using the corresponding key. They are two directions of the same reversible process, as NIST describes it.

What are the main types of encryption?

The two core types are symmetric, where one key does both jobs, and asymmetric, where a public key encrypts and a private key decrypts. Hybrid systems combine them. Within symmetric encryption, ciphers are either block or stream ciphers.

Which is faster, AES or RSA?

AES is much faster because it is symmetric. RSA and other asymmetric methods are substantially slower, so they are used for small items such as exchanging a key. The AES key then encrypts the actual data.

Is hashing the same as encryption?

No. Hashing is designed to be one-way, so you cannot recover the original from the digest. It is used for checksums, signatures and message authentication. Encryption is reversible by anyone with the right key.