RC4 is no longer considered secure for most any purpose.  There is known bias in the first few bytes of the cipher that can allow for key-recovery with enough messages sent with the same key.  In general you want &quot;head room&quot; in your ciphers such that the best attacks today are not just impractical, but wildly impractical, because attacks tend to get better over time.<p>RC4 was known to not have this &quot;head room&quot; for a while, and now is largely broken.