Is “6 bit packed ASCII” an effective encoding to obscure text data?

I wrote a routine for a former employer that took the low six bits of ASCII text and "compressed" by cramming the bits together, so that 4 bytes reduced to 3. This had the advantage of automatically folding lowercase to uppercase (not reversibly) with no computational effort. (Our text data was supposed to be just upper case letters, digits and punctuation. Can you say COBOL? I knew you could.) Note that I also ignored the first 32 ASCII characters as well. (They did not appear in the input data.)

Would this encoding method obfuscate text (where SHOUTING was acceptable) in a way that does not yield readily to simple analysis? The data would be encoded from 4 bytes down to 3 like this - (assume that we are only looking at the low 6 bits of every byte, the high 2 bits are just clipped off):

B1 = all 6 bits of first byte + low 2 bits of 2nd byte
B2 = "upper" 4 bits of 2nd byte + lower 4 bits of 3rd byte
B3 = last 2 bits of 3rd byte + all 6 bits of 4th byte


(Is there a prettier picture to illustrate this?)

• Short answer, no. This is similar to performing Base64 decode on plaintext data. You may have noticed that ASCII letters are actually 7 bits... – Richie Frame Jun 29 '16 at 23:17
• @RichieFrame Yes, but if you can sacrifice lower case, ignoring the two high bits leads to lowercase and uppercase being indistinguishable. Example: Uppercase A is hex 41, lowercase a is hex 61. "It's like, one bit different, you know?" I had an alternative algorithm which only ignored the top bit and compressed 8 bytes to 7... Oh, right, I ignored the whole first 32 ASCII characters as well. Gotta cut corners somehow. – user36481 Jun 29 '16 at 23:21
• as @A.Toumantsev says below, there isn't a good way to answer "is this effective" in the absence of real keyed encryption. What is the threat model? What resources does the attacker have? If I'm the attacker, you've already told me everything I need to know to decode the data. – bmm6o Jun 30 '16 at 23:59
• If you're comparing it with putting a lock on a diary, then yes this method of obfuscation will keep your little sister from reading your data. – bmm6o Jul 1 '16 at 15:18
• And I shouldn't have said that the type of question is unanswerable, it just needs to be more specific, like: How does this transformation affect the byte distribution. – bmm6o Jul 1 '16 at 15:19