ESI is not clobbered; no need to clear EDX as only DL is filled before and
it is overwritten before use.
Shellcodes in ruby modules not regenerated, but I guess you want to
regenerate them again anyway :-)
Provided as a block to be included into stagers and/or decoder stubs.
Also included is a test shellcode that can be used for verifying that the
algorithm is compatible to Ruby's OpenSSL RC4 algorithm.