Configuration

Algorithm

Accept any secret

Encryption secret (Base64)

Salt (Base64)

IV (Base64)

Padding

Mode

Data Encryption | AES-256

encoding / encryption

Base64 encoded

Text input

Output

—

Data Encryption

Encrypt and decrypt text with AES, Triple DES, RSA-OAEP, and several other ciphers, with control over the block mode and padding scheme. Useful for protecting a note, testing how a cipher behaves, or checking that two systems agree on the same parameters. Everything runs in your browser — your text and your keys are never transmitted.

Supported algorithms

AES is standardised as FIPS 197; the block modes it runs in come from NIST SP 800-38A. The older ciphers are included because real systems still emit them and something has to read that output, not because they are advisable for new work.

Ciphers offered here. Generated from the tool’s own registry, so it cannot list one it does not implement.
Algorithm	Kind	Definition
AES-128	Block cipher	AES-128 is the Advanced Encryption Standard with a 128-bit key: a widely used symmetric encryption algorithm designed to securely encrypt data. It is part of the AES family, which also includes AES-192 and AES-256, with the number referring to the key length in bits.
AES-192	Block cipher	AES-192 is the Advanced Encryption Standard with a 192-bit key, a symmetric encryption algorithm that is part of the AES family of encryption standards, which also includes AES-128 and AES-256.
AES-256	Block cipher	AES-256 is the Advanced Encryption Standard with a 256-bit key: the most secure variant of the AES encryption family, widely used for encrypting sensitive data.
DES	Block cipher	DES, the Data Encryption Standard, is an older symmetric encryption algorithm that was widely used for securing digital data, but is now considered obsolete due to its vulnerability to modern computing power.
TDES-112	Block cipher	TDES-112 is the Triple Data Encryption Standard with a 112-bit key: an enhanced version of the original DES encryption algorithm, designed to improve security by applying the DES algorithm three times with different keys.
TDES-168	Block cipher	TDES-168 is the Triple Data Encryption Standard with a 168-bit key: a more secure variant of the TDES encryption algorithm, offering stronger encryption than TDES 112 by using a 168-bit key (three separate 56-bit DES keys).
RABBIT	Stream cipher	Rabbit is a stream cipher designed for high-speed encryption, developed by the EU's eSTREAM project as part of its effort to find new and efficient encryption algorithms.
RC4	Stream cipher	RC4, or Rivest Cipher 4, is a widely used stream cipher developed by Ron Rivest in 1987. It became popular due to its simplicity, speed, and ease of implementation. RC4 encrypts data one byte at a time and uses a variable-length key, typically ranging from 40 bits to 2048 bits.
RC4-DROP	Stream cipher	RC4-DROP is a technique used to mitigate some of the weaknesses in the original RC4 stream cipher. Specifically, it involves discarding a number of initial keystream bytes generated by the key scheduling algorithm (KSA) before starting the actual encryption process. The "DROP" refers to dropping or ignoring the first few bytes of the keystream, which helps reduce certain biases and vulnerabilities present in the early part of the stream.
RSA-OAEP	Asymmetric cipher	RSA-OAEP is Rivest-Shamir-Adleman with Optimal Asymmetric Encryption Padding: an enhanced version of the RSA encryption algorithm that includes a secure padding scheme to improve its security. OAEP is used to prevent various attacks, such as chosen-plaintext attacks, by adding randomness and structure to the plaintext before encryption.

AES-128

General-purpose encryption: AES-128 is commonly used in a wide range of applications such as VPNs, file encryption, secure communications, and data protection.

AES-192

Middle-ground security: AES-192 is used in scenarios where a higher level of encryption is needed than AES-128 but without the computational cost of AES-256.
High-security applications: It is used in high-security applications like secure communications, data encryption and network security protocols.

AES-256

High-security applications: AES-256 is commonly used in high-security applications, such as military communications, government data protection, financial institutions, cloud storage encryption, and VPNs.

DES

Historical use: DES was historically used in financial transactions, government communications, and data storage systems. However, it has been largely replaced by more secure algorithms like AES.

TDES-112

Legacy financial systems: TDES 112 is used in legacy systems, especially in financial applications (e.g., ATM transactions, point-of-sale systems), where backward compatibility with DES is needed but enhanced security is required.

TDES-168

Banking and card data: TDES 168 is used in financial systems, legacy applications, and banking, especially for encrypting card data, ATM transactions and secure communications that need higher security than DES, but cannot yet migrate to AES.

RABBIT

High-throughput encryption: Rabbit is used in applications that require fast encryption and decryption of large amounts of data, like VPNs, wireless communications, and file encryption.

RC4

Historical use: RC4 was historically used in SSL/TLS for encrypting web traffic, WEP (Wired Equivalent Privacy) for wireless security, and Microsoft's RDP (Remote Desktop Protocol).

RC4-DROP

Hardening existing RC4 deployments: RC4 DROP is used in systems that still rely on RC4 but want to mitigate some of its known weaknesses.
Legacy protocols: It is sometimes applied in protocols like TLS or WEP (Wireless Encryption Protocol), although RC4 itself is now considered obsolete and insecure.

RSA-OAEP

Hybrid encryption: RSA with OAEP is used in modern cryptographic systems to provide enhanced security when encrypting small amounts of data, like symmetric encryption keys in hybrid encryption schemes.
Secure communication protocols: It is widely used in SSL/TLS for secure web communications, email encryption, and cryptographic protocols.

How your passphrase becomes a key

This tool derives keys the OpenSSL way, which is not a standard

AES-256 needs a 256-bit key, but you type a passphrase. Something has to bridge the two, and what this tool uses — via CryptoJS — is OpenSSL’s EVP_BytesToKey: a single pass of MD5 with an 8-byte salt and one iteration.

That is not a standard key derivation function. RFC 8018 specifies PBKDF2, and modern practice prefers Argon2id or scrypt, all of which are deliberately slow and iterate tens of thousands of times. One round of MD5 is fast, which is exactly the property you do not want between an attacker and your passphrase.

The practical consequence: ciphertext from this tool is only as strong as the passphrase itself against an offline guessing attack. Use a long random passphrase — the password generator makes one — and treat this tool as an inspector and a learning aid rather than as a vault.

It also explains an interoperability detail that otherwise looks like a bug: output from this tool decrypts with openssl enc and with other CryptoJS-based tools, but not with a library expecting PBKDF2, even given the same passphrase and cipher. The ciphertext is fine; the key derived from the passphrase differs.

Encryption is not encoding

Encryption transforms data so that it cannot be read without the correct key. That is what separates it from encoding: Base64 and URL encoding are public, keyless transformations that anyone can reverse instantly, and they provide no confidentiality at all. If you only need to make data safe to transmit as text, use the encoding tool instead.

The security of everything on this page rests entirely on the key. The algorithms are public and well documented — that is a feature, not a weakness. A cipher whose security depends on nobody knowing how it works has never held up in practice.

Symmetric and asymmetric

Symmetric ciphers

AES, DES, Triple DES, RC4, and Rabbit all use one key for both encryption and decryption. They are fast and handle data of any size, which makes them the workhorses of practical encryption. The difficulty is distribution: both parties need the same secret, and getting it to the other side securely is its own problem.

Asymmetric ciphers

RSA-OAEP uses a key pair — a public key that encrypts and a private key that decrypts. Anyone can encrypt a message to you using your public key, and only you can read it. That solves key distribution, but it is far slower and can only encrypt data smaller than the key size.

Real systems use both. TLS, the protocol securing this page, uses asymmetric cryptography to agree on a symmetric key, then switches to a symmetric cipher for the actual traffic. This is called hybrid encryption, and it takes the key-distribution advantage of one with the speed of the other.

Which algorithm to choose

AES-256— the default recommendation. It is the current standard, has withstood two decades of analysis, and is used everywhere from disk encryption to government classified material.
AES-128 and AES-192— also secure. AES-128 remains well beyond brute-force reach; the larger key sizes provide margin rather than fixing any known weakness.
Triple DES— legacy, and formally so: NIST SP 800-131Ar2 disallowed it for new encryption after 2023. It survives in older financial systems, but it is slow, and its 64-bit block makes a collision likely after about 32 GB under one key — the Sweet32 attack — which is a real limit rather than a theoretical one.
DES— broken. Its 56-bit key was brute-forced in the late 1990s and can now be exhausted quickly. Present here for interoperability with old data, not for protecting anything.
RC4— deprecated. Statistical biases in its output led to practical attacks, and it has been prohibited in TLS since 2015.
RSA-OAEP— the right choice for encrypting a small value, such as a symmetric key or a short credential, to a recipient's public key.

Block modes

A block cipher encrypts fixed-size blocks, so the mode determines how successive blocks relate to each other. This choice matters as much as the algorithm; all five below are specified in NIST SP 800-38A.

CBC— each block is combined with the previous ciphertext block before encryption, so identical plaintext blocks produce different output. The common default.
CFB and OFB— turn a block cipher into a stream cipher, allowing encryption of data that is not a whole number of blocks.
CTR— encrypts a counter and combines the result with the plaintext. Parallelizable and widely used in modern protocols. CTR Gladman is a variant implementation.
ECB— encrypts each block independently, with no chaining. This is its weakness: identical plaintext blocks give identical ciphertext, so structure in the original data survives into the output. It should be avoided for anything real.

Padding

Block ciphers need input that fills a whole number of blocks, so shorter data is padded. PKCS7 is the standard choice and is what most systems expect. ANSI X9.23, ISO 10126, and ISO 97971 are alternatives specified by other standards.

Zero padding cannot be unambiguously removed if the data legitimately ends in zero bytes, and "none" requires input that already fills the block exactly. Both are for specific interoperability cases rather than general use.

Common uses

Protecting a note or credential— encrypt text before storing it somewhere you do not fully trust.
Testing interoperability— confirm that two systems agree on algorithm, mode, and padding.
Learning how ciphers behave— see directly how changing the mode or padding changes the output.
Decrypting legacy data— read values produced by older systems that used DES or Triple DES.
Verifying an implementation— check output against a known-good reference before shipping code.

Practical cautions

The key is everything.A weak or guessable key defeats any algorithm. Use a long random key — the password generator will produce one.
Lose the key, lose the data.There is no recovery mechanism. This is the point of encryption, and it cuts both ways.
Encryption alone does not prove authenticity.These modes protect confidentiality but do not detect tampering. Modern protocols use authenticated encryption, such as AES-GCM, to cover both.
Match every parameter.Decryption requires the same algorithm, key, mode, and padding. Mismatched settings produce failure or nonsense rather than a helpful error.
For serious needs, use a vetted tool.A password manager or full-disk encryption handles key management, authentication, and secure storage — concerns beyond what any single-purpose page can address.

Frequently asked questions

Is my data or key sent to a server?

No. Encryption and decryption run entirely in your browser. Nothing you type here is transmitted, logged, or stored, and refreshing the page discards it.

Which algorithm should I use?

AES-256 unless you have a specific reason to do otherwise. It is secure, fast, and universally supported. Choose RSA-OAEP only when you need public-key encryption of a small value.

Why is DES still offered if it is broken?

For reading old data. Systems encrypted with DES decades ago still exist, and decrypting their output requires the algorithm. It should never be used to protect anything new.

Can AES-256 be broken?

Not by brute force with any foreseeable technology — the key space is around 10⁷⁷. Real-world compromises come from weak keys, poor implementation, or key theft, not from breaking the cipher itself.

Why does the same input give different output each time?

Because a good cipher introduces randomness, usually through an initialization vector, so that repeated encryption of identical plaintext produces different ciphertext. This is deliberate: it prevents an observer from spotting that the same message was sent twice.

What if decryption returns nothing useful?

Almost always a parameter mismatch — a different key, mode, or padding than was used to encrypt. Decryption with the wrong settings does not report an error; it simply produces meaningless bytes. That silence is a property of unauthenticated modes: with no integrity check, there is nothing to fail.

Standards and references

FIPS 197 Advanced Encryption Standard (AES) 2001
NIST SP 800-38A Recommendation for Block Cipher Modes of Operation: Methods and Techniques 2001
NIST SP 800-38D Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) 2007
RFC 8018 PKCS #5: Password-Based Cryptography Specification Version 2.1 2017
NIST SP 800-131Ar2 Transitioning the Use of Cryptographic Algorithms and Key Lengths 2019

Data Encryption | AES-256

Data Encryption

Supported algorithms

AES-128

AES-192

AES-256

DES

TDES-112

TDES-168

RABBIT

RC4

RC4-DROP

RSA-OAEP

How your passphrase becomes a key

Encryption is not encoding

Symmetric and asymmetric

Symmetric ciphers

Asymmetric ciphers

Which algorithm to choose

Block modes

Padding

Common uses

Practical cautions

Frequently asked questions

Standards and references

We use cookies