Encryption from text to base64. Ddecryption from base64 to text. Key - text.

RC4 - (Rivest Cipher 4, also known as ARC4 or ARCFOUR, which means Assumed RC4) stream cipher based on parameterized key generator of pseudo-random bits with uniform distribution. High speed operation and variable key size. Despite its simplicity and speed in software, RC4 has detected many vulnerabilities, making it unsafe. This is especially true when the start of the output key stream is not discarded, or when non-random or related keys are used. Particularly problematic was the use of RC4 lead to very insecure protocols such as WEP.

As of 2015, there is an assumption that some government cryptographic agencies may have the ability to violate RC4 when using the TLS Protocol. IETF has published RFC 7465 to prohibit the use of RC4 in TLS; Mozilla and Microsoft have released similar guidelines.

Several attempts have been made to strengthen the RC4 algorithm, in particular Spritz, RC4A, VMPC, and RC4+.