RC4 (Rivest Cipher 4) is a symmetric stream cipher designed by Ron Rivest in 1987. It was widely used in WEP, WPA, SSL/TLS (RC4 cipher suite), and software like Adobe Acrobat. It is now considered insecure and has been removed from all modern protocols.

RC4 has multiple known biases in its keystream output that allow statistical attacks to recover plaintext. The RC4 cipher suite was prohibited in TLS 1.3 and banned by RFC 7465 in 2015.

RC4 Stream Cipher — Rivest Cipher 4 Encrypt & Decrypt

How to Use rc4-cipher

Paste or enter your input into the text field.
Configure any options (format, delimiter, encoding, or mode) using the controls above the output.
The result updates instantly — no submit button required for most operations.
Click Copy or Download to take the output to your next step.

RC4 (Rivest Cipher 4) stream cipher — for testing legacy systems. Free and browser-based — everything runs in your browser's JavaScript engine with no data sent to any server.

How rc4-cipher Works

rc4-cipher is a browser-side security utility built for speed and simplicity. Paste your input and the result appears within milliseconds. The tool handles edge cases — empty inputs, special characters, large datasets — without crashing or producing silent incorrect output. If you need a related operation, check the Related Tools section below.

Accepts large inputs — no size limits imposed by this tool
Handles edge cases: empty fields, special characters, and Unicode
Copy-to-clipboard and file download for every output
Works on Chrome, Firefox, Safari, and Edge without any extensions

Frequently Asked Questions

What does rc4-cipher do?

rc4-cipher rc4 (rivest cipher 4) stream cipher — for testing legacy systems. Results appear immediately — no page reloads, no waiting for a server response.

What input does rc4-cipher accept?

Paste text directly into the input field, or type your data. Most operations handle Unicode, special characters, and multi-line inputs without issue.

How large an input can I process?

There is no hard limit imposed by this tool. Very large inputs (multi-MB text) process within your browser's available memory. For files larger than 50 MB, a command-line tool may be faster.

Can I download the output?

Yes — every output panel includes a Copy to Clipboard button and a Download as file option. Outputs are saved as plain text or the appropriate file format for the operation.

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RC4 Encrypt & Decrypt online

RC4 (Rivest Cipher 4) stream cipher — for testing legacy systems — runs in your browser