Full Disclosure: Re: Cipher detection

[Tim <tim-security () sentinelchicken org>]

> Here're some more examples:
>
> dummy () example com GGobQ2bsqd64PXVAmaDiDBg=
> eummy () example com GWobQ2bsqd64PXVAmaDiDBg=
> dummy () example co  GGobQ2bsqd64PXVAmaDiDA==
> dummy () example @ex GGobQ2bsqd64PXVAmaDBBg0=
> dummy             GGobQ2Y=
> dumm              GGobQw==
> eummy             GWobQ2Y=
> eumm              GWobQw==
> example.com       GWcXQ2/AqYi6P2g=
> dxample.com       GGcXQ2/AqYi6P2g=
> 11111 () example com TS5HHy7sqd64PXVAmaDiDBg=
> 11111             TS5HHy4=
>
> Looks like a base64+xor, am I right? And that's enough information for me. 

Yes, it is looking like a fixed key stream XORed with the plaintext.
Note that this could mean they're using any number of "good"
encryption algorithms (block cipher in OFB mode, stream cipher) with a
fixed IV.  This means the encryption is very broken, but it doesn't
necessarily mean they are using some half-baked custom obfuscation
technique.  They could be, but be careful with your accusations.

HTH,
tim

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