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Board Development & Technical Discussion
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BIP39 Calculate checksum
by
Sanglotslongs2
on 16/12/2020, 22:34:31 UTC
⭐ Merited by LoyceV (4) ,o_e_l_e_o (2) ,Heisenberg_Hunter (1) ,ETFbitcoin (1) ,vapourminer (1)
Hello,

I want to calculete checksum for a BIP 39 seed by hand. All my 11 first word are generated by Dice, but for the last word I need to do a checksum (no worry just a fake seed)


I have this 11 words :

Word          n°List       N°list in binary
possible      1348      10101000100
wage         1969      11110110001
deliver         464         00111010000
gossip         807         01100100111
first         699         01010111011
party         1284      10100000100
hair         834         01101000010
antique         79         00001001111
salute         1526      10111110110
fuel         751         01011101111
survey         1749      11011010101
miracle         1131         10001101011   <==== I Need to find Him


Here the entropy for my 11 words :
1010100010011110110001001110100000110010011101010111011101000001000110100001000 001001111101111101100101110111111011010101
Here the correct 12words entropy :
1010100010011110110001001110100000110010011101010111011101000001000110100001000 0010011111011111011001011101111110110101011000110
Checksum that I must found:
1011



So my final seed must be :
1010100010011110110001001110100000110010011101010111011101000001000110100001000 00100111110111110110010111011111101101010110001101011

So the last 11bits "10001101011" are in decimal "1131" corresponding here to "miracle"

If understand this https://learnmeabitcoin.com/technical/mnemonic page :
"This checksum is created by hashing the entropy through SHA256, which gives us a unique fingerprint for our entropy. We then take 1 bit of that hash for every 32 bits of entropy, and add it to the end of our entropy."


So I have my 11 words entropy :
1010100010011110110001001110100000110010011101010111011101000001000110100001000 001001111101111101100101110111111011010101
I hash it to SHA-256 with hex result :
4C3FA7A784B345C6BA9ECA9FCFEEAF36E9BE00D0A2406B88DB61F609137B8F68
Convert it to binary :
1001100001111111010011110100111100001001011001101000101110001101011101010011110 1100101010011111110011111110111010101111001101101110100110111110000000001101000 0101000100100000001101011100010001101101101100001111101100000100100010011011110 111000111101101000

Where do I find "10001101011" ?

Is it possible to predict the checksum with my 11 words ? Or do I need to bruteforce ?