bign256: digital signature algorithm (#935) #193

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 6s
build (1.65.0, wasm32-unknown-unknown)	1m 5s
cross (armv7-unknown-linux-gnueabihf, 1.65.0)	2m 24s
build (stable, thumbv7em-none-eabi)	15s
build (stable, wasm32-unknown-unknown)	13s
cross (armv7-unknown-linux-gnueabihf, stable)	1m 37s
doc	25s
cross (aarch64-unknown-linux-gnu, 1.65.0)	2m 15s
cross (aarch64-unknown-linux-gnu, stable)	1m 25s
test (i686-unknown-linux-gnu, 1.65.0, sudo apt update && sudo apt install gcc-multilib)	2m 41s
cross (powerpc-unknown-linux-gnu, 1.65.0)	2m 16s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	1m 22s
cross (powerpc-unknown-linux-gnu, stable)	1m 22s
test (x86_64-unknown-linux-gnu, 1.65.0)	1m 53s
test (x86_64-unknown-linux-gnu, stable)	1m 1s
	21m 20s

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