can't install cowpatty under 8.10

[刘先良]

i want to install cowpatty ,but when i "make" there's something wrong!
here is the details:

ethan at King-laptop:~/cowpatty-4.3$ make
cc -pipe -Wall -DOPENSSL  -O2 -g3 -ggdb   -c -o md5.o md5.c
md5.c:20:25: error: openssl/md5.h: No such file or directory
md5.c: In function ‘md5_mac’:
md5.c:28: error: ‘MD5_CTX’ undeclared (first use in this function)
md5.c:28: error: (Each undeclared identifier is reported only once
md5.c:28: error: for each function it appears in.)
md5.c:28: error: expected ‘;’ before ‘context’
md5.c:29: warning: implicit declaration of function ‘MD5_Init’
md5.c:29: error: ‘context’ undeclared (first use in this function)
md5.c:30: warning: implicit declaration of function ‘MD5_Update’
md5.c:33: warning: implicit declaration of function ‘MD5_Final’
md5.c: In function ‘hmac_md5_vector’:
md5.c:40: error: ‘MD5_CTX’ undeclared (first use in this function)
md5.c:40: error: expected ‘;’ before ‘context’
md5.c:48: error: ‘context’ undeclared (first use in this function)
make: *** [md5.o] Error 1

i have installed openssl and "aptitude install libssl-dev", who can help
me?

ps: cowpatty come from http://www.willhackforsushi.com/Cowpatty.html