RC4 Encryption and Decryption

RC4 online encryption and decryption tool, providing fast and easy-to-use encryption and decryption services for RC4 symmetric stream cipher.

Green Tool

⚠️ 注意：RC4 是流密码

流密码不使用加密模式(Mode)和填充模式(Padding)，这些选项将被忽略。

流密码逐字节加密数据，无需分块和填充。

生成结果：

Hex	--
Base64	--

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RC4 stream cipher encryption decryption

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Tool Introduction

The RC4 Encryption and Decryption tool is a convenient and fast online service for performing encryption and decryption operations using the RC4 (Rivest Cipher 4) stream cipher. RC4 is a widely used symmetric stream cipher algorithm, known for its simple implementation and high speed. This tool allows users to input plaintext for encryption or ciphertext for decryption, along with a key, to instantly obtain the encrypted or decrypted result, making it an ideal choice for learning and testing the RC4 algorithm.

RC4 Stream Cipher Principle

RC4 (Rivest Cipher 4) is a stream cipher algorithm designed by Ron Rivest in 1987. It is known for its high efficiency and simplicity in software implementation. The core of RC4 includes two main phases: the Key-Scheduling Algorithm (KSA) and the Pseudo-Random Generation Algorithm (PRGA). The KSA phase initializes a 256-byte state vector S based on the user-provided key. The PRGA phase continuously swaps elements in S and selects a byte from it as the keystream output. The keystream is crucial for encryption by XORing with the plaintext, or for decryption by XORing with the ciphertext. Since the keystream is uniquely generated based on the key, encryption and decryption use the same keystream, making RC4 a symmetric encryption algorithm.

How to Use

Enter Plaintext/Ciphertext: Paste or type the plaintext you wish to encrypt, or the ciphertext you need to decrypt, into the corresponding input box.
Enter Key: Enter the key used for encryption or decryption into the key input box. Please ensure the same key is used for both encryption and decryption; otherwise, decryption will not be successful. The strength of the key directly affects the security of the encryption.
Select Operation: Click the “Encrypt” button to perform encryption, or the “Decrypt” button to perform decryption.
Get Result: The tool will immediately display the encrypted ciphertext (usually in hexadecimal representation) or the decrypted plaintext in the output box.

Input Parameter Requirements:

Text Content: Supports any UTF-8 encoded text string as plaintext or ciphertext input.
Key: Supports any UTF-8 encoded text string as the key. A moderate key length is recommended; overly short keys will reduce security, but overly long keys offer no additional benefit as RC4 will process them internally.

Output Result Format:

Encrypted ciphertext is usually displayed as a hexadecimal string for easy transmission and storage.
Decrypted plaintext will be displayed directly in the output area as the original text string.

Frequently Asked Questions

Q: What type of encryption algorithm is RC4?
A: RC4 is a symmetric stream cipher algorithm. Symmetric means that encryption and decryption use the same key; stream cipher means it encrypts data streams byte by byte or bit by bit.
Q: What input formats does this tool support?
A: This RC4 encryption/decryption tool primarily supports text (strings) as input for plaintext, ciphertext, and keys. Internal processing converts them into byte sequences for encryption.
Q: What is the format of the output result?
A: Encrypted ciphertext is usually displayed as a hexadecimal string for easy viewing and copying. Decrypted results will be displayed as the original text string.
Q: Is the RC4 algorithm secure?
A: The RC4 algorithm has some known security weaknesses, such as statistical biases in the initial bytes of the keystream, which can lead to certain attacks. Therefore, RC4 is no longer recommended for modern applications requiring very high security. This tool is more suitable for learning RC4 principles, testing, or scenarios with lower security requirements.

Important Notes

Key Management: RC4 is a symmetric algorithm that relies on a key for encryption and decryption. Please ensure your key is properly managed and never disclosed to unauthorized third parties. If the key is lost or stolen, data faces the risk of being unrecoverable or maliciously decrypted.
Character Encoding: When using this tool, it is recommended to consistently use UTF-8 encoding for plaintext, ciphertext, and keys. Inconsistent encoding may lead to incorrect encryption results or garbled text after decryption.
Security Considerations: Given RC4's known security vulnerabilities and limitations, for applications requiring high-strength data protection (such as sensitive business data or personal privacy information), it is strongly recommended to consider using more modern and secure symmetric encryption algorithms, such as AES (Advanced Encryption Standard). This RC4 encryption and decryption tool is primarily intended for educational, debugging, or low-security-demand scenarios.