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Perform RC4 stream cipher encryption and decryption online. Supports direct text input and secret key management.
Please enter content and click Encrypt/Decrypt.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
RC4 is a symmetric stream cipher: encryption combines input bytes with a generated keystream, and decryption uses the same key stream to recover bytes. This page accepts text for encryption and Base64 or hexadecimal ciphertext for decryption. The key can be entered as text, Hex, or Base64. Text is interpreted as UTF-8 bytes, while Hex and Base64 strings are decoded into bytes.
The selected key length is one of 40, 56, 64, 80, 128, or 256 bits; the default is 128 bits. The decoded key must match the selected length. When encrypting text, the output appears in both Hex and Base64. These are two encodings of the same ciphertext bytes, not different ciphers. When decrypting, choose the ciphertext’s actual encoding and use the same key bytes as encryption.
RC4 is suitable here only for understanding a legacy format or checking compatibility. RFC 7465 prohibits RC4 cipher suites in TLS because of known weaknesses. RFC 6229 publishes test vectors for comparing compatible implementations.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
For encryption, enter readable text or select another supported input representation. For decryption, identify whether the saved ciphertext is Hex or Base64 before pasting it.
Select Text, Hex, or Base64 to match the key material. Text is encoded as UTF-8. Hex must represent byte pairs; Base64 is decoded before the tool checks its byte length.
Choose the key size used by the legacy system. The decoded key has to contain exactly the number of bytes implied by the selected bit length; for example, 128 bits corresponds to 16 bytes.
Encryption returns Hex and Base64 views of the ciphertext. During decryption, set the input encoding correctly and inspect the recovered text. If the original bytes were not UTF-8 text, the text view may be unreadable even when the byte output is useful.
Use cases
See how the tool fits into real work and everyday tasks.
Use a non-sensitive sample and known key to compare output with documented test vectors or a compatible legacy application. Match the byte encoding and key length exactly.
Encrypt a short, harmless phrase and decrypt the resulting bytes with the same key. The exercise helps distinguish a cipher operation from Hex or Base64 encoding.
When you already have the correct key for data you are authorized to access, try the documented legacy format. A readable result alone does not establish that the data is authentic or unchanged.
Q&A
Find concise answers to common questions and confusing cases.
They encode the same output bytes using different alphabets. Converting between them changes the text representation, not the ciphertext or the cipher strength.
Check whether the other system interprets the key as UTF-8 text, Hex, or Base64. Also compare the exact key bytes, ciphertext encoding, and plaintext encoding. The same visible characters can represent different bytes under different formats.
The displayed text assumes UTF-8. If the original plaintext was binary or used another character encoding, inspect the returned bytes in Hex or Base64 instead.
No. RC4 does not add an authentication tag in this tool. A result that appears readable does not prove who created it or whether it was altered.
Notes
Review scope, result limitations, and important precautions before use.
Do not use RC4 for new systems, passwords, payment information, private communications, or other sensitive content. Its known weaknesses remain even when a longer key is selected.
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