I think you are missing dependencies from the ssl library. Have a look into the docs [1].
Your questions implies that you are not very experienced in C coding.
Maybe you should ask yourself the question if starting with a complex and potential security risky api like openssl is the right thing for a beginner.
Happy coding
[1] https://www.openssl.org/docs/manmaster/ssl/ssl.html
sorry, my mistake about the package (I use debian testing)
find /usr/include -name md5.h
find /usr/include/ -name md5.h
/usr/include/openssl/md5.h
/usr/include/crypto++/md5.h
#include <openssl/md5.h>
now I've many errors
thanks for help!
alice.c:50:18: error: unknown type name ‘md5_context’
void md5_starts( md5_context *ctx )
^
alice.c:61:19: error: unknown type name ‘md5_context’
void md5_process( md5_context *ctx, uint8 data[64] )
^
alice.c:61:37: error: unknown type name ‘uint8’
void md5_process( md5_context *ctx, uint8 data[64] )
^
alice.c:184:18: error: unknown type name ‘md5_context’
void md5_update( md5_context *ctx, uint8 *input, uint32 length )
^
alice.c:184:36: error: unknown type name ‘uint8’
void md5_update( md5_context *ctx, uint8 *input, uint32 length )
^
alice.c:184:50: error: unknown type name ‘uint32’
void md5_update( md5_context *ctx, uint8 *input, uint32 length )
^
alice.c:223:8: error: unknown type name ‘uint8’
static uint8 md5_padding[64] =
^
alice.c:231:18: error: unknown type name ‘md5_context’
void md5_finish( md5_context *ctx, uint8 digest[16] )
^
alice.c:231:36: error: unknown type name ‘uint8’
void md5_finish( md5_context *ctx, uint8 digest[16] )
^
alice.c: In function ‘main’:
alice.c:299:3: error: unknown type name ‘md5_context’
md5_context ctx;
^
alice.c:321:3: warning: implicit declaration of function ‘md5_starts’ [-Wimplicit-function-declaration]
md5_starts( &ctx );
^
alice.c:325:7: warning: implicit declaration of function ‘md5_update’ [-Wimplicit-function-declaration]
md5_update( &ctx, buf, i );
^
alice.c:332:3: warning: implicit declaration of function ‘md5_finish’ [-Wimplicit-function-declaration]
md5_finish( &ctx, md5sum );
^
Pol