Is it possible for sha1 hashes to end with zero bytes?
Python Code
hash = haslib.sha1();
hash.update(STRING THAT RESULTS IN ZERO BYTES);
if hash.digest().endswith('\x00\x00\x00'):
....
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This property is for SHA-256 actually used in bitcoin mining (although I think BC hashes are tested to start with zero bits, but as either bit is as likely to be 0 that doesn't matter much). – Maarten Bodewes Nov 28 '15 at 23:05
1 Answers
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Yes, since hash function outputs are supposed to be uniformly distributed you have a non-zero chance of getting any supported output. The chance for seeing the last 24 bits (3 byte) as zero is 1.0/(2**24) or 5.9 * 10-8. On average you will have to try 223 random strings to find one with this property. Since hashing is pretty fast, this shouldn't take longer than a couple of minutes (although, Python might be a bit slow in general).
Artjom B.
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Thank you! The only possibility to find a matching hash is brute forcing.. isn't it? – themz Nov 28 '15 at 21:26
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Yes, exactly. You would have to brute-force your way to that result. – Artjom B. Nov 28 '15 at 21:27
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1Running a simple (32 bit) counter and hashing that should be enough to find such a hash. Again, that's what BC does. – Maarten Bodewes Nov 28 '15 at 23:08