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 Feb 17 awarded Popular Question Feb 2 comment Breaking a PRNG Scheme @jspencer, That would be a way to reduce the bias! Nonetheless, I'd like to know if the introduction of the bias, however small, could allow an attacker to gain knowledge in such a way to predict the subsequent numbers from the stream (or whether they will be within a threshold). Jan 31 revised Breaking a PRNG Scheme Edited latex code to be prettier. Jan 31 comment Breaking a PRNG Scheme Correct me if I'm wrong, is not the probability that the last 3 hex characters are used equal to $\left(\frac{1048575-999999}{1048575}\right)^{25}$? Jan 31 comment Breaking a PRNG Scheme How can I clarify the algorithm in the case of the upper 3 digits? Here's my attempt: assume all 25 five-character hex-strings are >=1,000,000 in decimal. Convert the remaining 3-character hex-string to decimal that will have a range of [0,4096). Divide this by 100, yielding a range of [0,40.96) and return the result. Jan 31 suggested approved edit on Breaking a PRNG Scheme Jan 31 revised Breaking a PRNG Scheme added 29 characters in body Jan 31 comment Breaking a PRNG Scheme @figlesquidge, Sorry for all this confusion. The output should be in [0,100) with two-decimal precision (e.g. 40.96). Jan 30 comment Breaking a PRNG Scheme Forgive me, what is the meaning of "Let S = {min((t[19:0])/10000, 99) | t in T}", specifically, "t[19:0]"? Jan 30 comment Breaking a PRNG Scheme @jspencer, fgrieu informed me that when we say "in decimal" we're implying division by 100. Therefore, where it says "the remaining 3 hex digits are returned (in decimal)" the meaning "convert to decimal by division of 100 and representation of digits [0-9]" is implied. Jan 27 revised Breaking a PRNG Scheme edited tags Jan 21 revised Breaking a PRNG Scheme deleted 47 characters in body Jan 21 comment Breaking a PRNG Scheme I could see constructing a distinguisher that identifies this scheme vs. an actual RNG based on the fact that numbers [0,40.95] will appear slightly more often than others. Other than that, I'm still unsure of how to relate the distinguisher to predicting >=50 on return. Jan 21 comment Breaking a PRNG Scheme No, SHA256 on key, HMAC512 on message, key. Jan 21 revised Breaking a PRNG Scheme deleted 33 characters in body Jan 21 revised Breaking a PRNG Scheme edited body Jan 21 revised Breaking a PRNG Scheme deleted 1 characters in body Jan 21 awarded Editor Jan 21 revised Breaking a PRNG Scheme /larger/smaller, />/>= Jan 21 asked Breaking a PRNG Scheme