Quote from: alek76 on Today at 09:34:06 AM

Quote from: nomachine on Today at 08:27:11 AM

result
0230210c23b1a047bc9bdbb13448e67deddc108946de6de639bcc75d47c0216b1b
Grin

Check each function separately. Starting with void point_add().
Missing intermediate variables.
   mpz_t imod;
   mpz_t l;
   mpz_t lsq;
   mpz_t lsq2;
   mpz_t lsq3;
   mpz_t mul;
   mpz_t x3;
   mpz_t xmx3;
   mpz_t xsub;
   mpz_t ymul;
   mpz_t ys;
   mpz_t ysub;

Should the results be stored in temporary variables?
For example:
mpz_sub(ysub, other.m_y, m_y);
mpz_sub(xsub, other.m_x, m_x);
mpz_invert(imod, xsub, m_curve.m_p);
mpz_mul(mul, ysub, imod);
mpz_mod(l, mul, m_curve.m_p);
mpz_pow_ui(lsq, l, 2);
mpz_sub(lsq2, lsq, m_x);
mpz_sub(lsq3, lsq2, other.m_x);
mpz_mod(x3, lsq3, m_curve.m_p);
mpz_sub(xmx3, m_x, x3);
mpz_mul(ymul, l, xmx3);
mpz_sub(ys, ymul, m_y);
mpz_mod(m_y, ys, m_curve.m_p);
mpz_set(m_x, x3);
mpz_set_ui(m_o, 0);

Did it. Now I have
# ./test.bin
Floating point exception

now I'm debugging to find out why
# gdb ./test.bin ./core.9180
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Reading symbols from ./test.bin...
[New LWP 9180]
Core was generated by `./test.bin'.
Program terminated with signal SIGFPE, Arithmetic exception.
#0 0x00007f962643fce1 in raise () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0 0x00007f962643fce1 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f96267b4867 in __gmp_exception () from /lib/x86_64-linux-gnu/libgmp.so.10
#2 0x00007f96267b488e in __gmp_divide_by_zero () from /lib/x86_64-linux-gnu/libgmp.so.10
#3 0x00007f96267ce4f5 in __gmpz_tdiv_r () from /lib/x86_64-linux-gnu/libgmp.so.10
#4 0x00007f96267c7760 in __gmpz_mod () from /lib/x86_64-linux-gnu/libgmp.so.10
#5 0x000055685a4666d6 in point_double (x=0x7ffdcc41f870, y=0x7ffdcc41f860, lmbda=0x7ffdcc41f850,
x3=0x7ffdcc41f840, y3=0x7ffdcc41f830, p=0x55685a469240 <p>) at test.cpp:97
#6 0x000055685a4665b8 in point_multiply (Qx=0x7ffdcc41f8e0, Qy=0x7ffdcc41f8d0, x=0x55685a469220 <Gx>,
y=0x55685a469230 <Gy>, k=0x7ffdcc41f8c0, p=0x55685a469240 <p>) at test.cpp:74
#7 0x000055685a466350 in private_key_to_public_key (private_key=0x55685a46712b "30568377312064202855",
compressed_public_key=0x7ffdcc41f900 "\001") at test.cpp:29
#8 0x000055685a466eb6 in main () at test.cpp:201
(gdb)

This is pain in ass Grin