While reverse engineering a database middleware. This is presumably encoding a list of double or float values with Base64 encoding and then compressing it.

Via zlib.decompress() I was able to decompress it, but I got a string of presumably multiple base64-strings. I can see that it consists of more than one, because it contains multiple =. But afaik, these do not always mark the end of a b64-encoded string, because one can also end without a =.

This is a excerpt of one field:


As an amateur on this field, I am very unsure where to start. From the documentation I know, that it's a b64-encoded list, but I don't know how to use it. Obviously, when decoded, it will consist of a binary format that in some computer language represents a list of floats.

Any tips on how to continue working on this problem? Unfortunately I have no access to the software currently, the only thing I have is this data structure.

Sorry for my amateur questions, and thanks in advance for any tips!

  • 2
    A Base64 string will not have \x12.....\xf4 etc hope i am not understanding wrong here
    – blabb
    Oct 26, 2021 at 17:49

1 Answer 1


The data you have here is not base64 encoded, as that would only have letters, numbers, +, /, and (as you mentioned) =. The \x escape code in the string indicates bytes that are non-printable or outside the ASCII range.

The regular pattern of = or near-= values (;, <, =, >) every four bytes suggests that this is a simple array of 4-byte little-endian fields with values relatively close to each other. Here is what it looks like as a 4-byte (single precision) float array.

>>> data = b'<\x12u<\xf4\x808=\x95\xf0U=\x9fse;\xef\xbe\xf2=A\xd1K=...'
>>> struct.unpack_from('<{}f'.format(str(len(data)//4)), data)
(0.014957960695028305, 0.045044854283332825, 0.05223139002919197, 0.003501154249534011, 0.11852823942899704, 0.049760106950998306, 0.07483314722776413, 0.07962337881326675, 0.0231693834066391, 0.05004388839006424, [...])

Does this look like the range of values you are expecting?

  • That's exactly what I was looking for, yes! Thanks! Quick noob question: How do you acquire this knowledge about the patterns? Any specific books, or is it just experience? Nov 24, 2021 at 12:56

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