RC Series (RC2/RC4/RC5/RC6) Online Encryption/Decryption
RC series symmetric encryption algorithms designed by Ron Rivest, supporting RC2, RC4, RC4-Drop, RC5 and RC6
Security Warning
RC2 has known vulnerabilities and is deprecated. Use only for legacy system compatibility.
Limit key search space (historical export compliance parameter)
About RC Cipher Suite
The RC cipher series was designed by Ron Rivest of MIT and RSA Security. 'RC' originally stood for 'Rivest Cipher' or 'Ron's Code'. The series includes RC2, RC4, RC5, and RC6, each with distinct characteristics.
RC2 is a 64-bit block cipher designed in 1987. RC4 is a stream cipher once widely used in SSL/TLS and WEP. RC5 introduced a novel parameterized structure. RC6 was designed as an AES candidate algorithm, enhancing diffusion through integer multiplication.
Algorithm Comparison
| Algorithm | Type | Key Length | Block Size | Security | Status |
|---|---|---|---|---|---|
| RC2 | Block Cipher | 1-128 bytes | 64 bits | Weak | Deprecated |
| RC4 | Stream Cipher | 1-256 bytes | N/A (stream) | Weak | Deprecated |
| RC5 | Block Cipher | 0-255 bytes | 32/64/128 bits | Good | Secure |
| RC6 | Block Cipher | 16/24/32 bytes | 128 bits | Excellent | AES Finalist |
RC2 (Rivest Cipher 2)
RC2 is a 64-bit block cipher designed in 1987. It uses variable-length keys (1-128 bytes) and has a unique 'effective key bits' parameter that can limit the key search space.
Originally designed as proprietary, RC2 was intended to achieve export compliance with 40-bit effective key length. Due to known vulnerabilities, it should only be used for legacy system compatibility.
RC4 (Rivest Cipher 4)
RC4 is a stream cipher designed in 1987. It generates a pseudorandom byte stream (keystream) that is XORed with the plaintext. Known for simplicity and speed, it was widely used in SSL/TLS, WEP, and WPA protocols.
Due to discovered vulnerabilities (particularly in the first few bytes of the keystream), RC4 has been deprecated from modern security protocols. The 'RC4-Drop' variant mitigates these issues by discarding initial keystream bytes.
RC5 (Rivest Cipher 5)
RC5 was published in 1994, introducing a parameterized design with three variables: word size (w), number of rounds (r), and key length (b). This flexibility allows RC5 to adapt to different security requirements.
RC5 uses data-dependent rotation as its primary nonlinear operation, simple yet effective. Common configurations include RC5-32/12/16 (32-bit word size, 12 rounds, 16-byte key).
RC6 (Rivest Cipher 6)
RC6 was submitted as an AES candidate in 1998, one of five finalists. It extends RC5 with integer multiplication for better diffusion and uses four working registers instead of two.
RC6 has a fixed 128-bit block size, supports 128/192/256-bit keys, and provides excellent security. Although Rijndael was selected as AES, RC6 remains a respected and secure algorithm.