Post
Topic
Board Development & Technical Discussion
Re: Fees associated with Taproot script spend
by
ppbened45
on 27/03/2025, 09:06:38 UTC
Hi I have a question related fees ( basically Virtual Size):

When I use let's say 3-of-5 signatures embedded on a Huffman tree composed on 3-of-3, and assuming we have only one input transaction and one output transaction, the first user to sign will need to decide the "transaction fee", in the software I run a "simulation" were I "sign" all the branches, so I end with the following values for the Virtual Size:
[203,203,203,203,211,211].

If instead I'm doing a 5-of-10, this is the list of virtual sizes:
[252,293,325,349,373,381,413,445,469,493,501,525,549,573,581,597,621,629,645,653,669,693,725,749,773,781,805,829,853,861,877,901,909,925,933,949,965,989,1013,1021,1037,1061,1069,1085,1093,1109,1117,1141,1149,1165,1173,1189,1197,1205,1221,1229,1253,1285,1309,1333,1341,1365,1389,1413,1421,1437,1461,1469,1485,1493,1509,1525,1549,1573,1581,1597,1621,1629,1645,1653,1669,1677,1701,1709,1725,1733,1749,1757,1765,1781,1789,1805,1829,1853,1861,1877,1901,1909,1925,1933,1949,1957,1981,1989,2005,2013,2029,2037,2045,2061,2069,2077,2101,2109,2125,2133,2149,2157,2165,2181,2189,2197,2205,2221,2229,2237]

Since the first user needs to decide the transaction fee, we are suggesting the user to use the "biggest" values, for a 3-of-5 would be 211, for a 5-of-10 would be 2237, since we don't know who from the rest of the users is signing next.

My question is, is this correct? I'm I correct in suggesting the higher values?
Because the alternative would be any posible value, but if turn out that the final combinations has a Virtual Size equal to the biggest one, then the transaction will never commit to the node.






Hey Angelo, yeah, you're right to suggest the highest virtual size since you don’t know which signing path will be taken, and this ensures the transaction always has enough fees to go through. The alternative could mean underpaying and the transaction getting stuck, so playing it safe makes sense.