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 Am 15.07.2016 12:07 nachm. schrieb "Pol Hallen" <de...@fuckaround.org>: 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
