Hi Jay, Thanks for your reply. Our requirement is as follows 1. only using openssl for authenticaion and a key wrap algorithm. No encryption is needed. 2. For MAC alogorithm, we need to use M_SHA1 / M_SHA256 For key wrap algo, we need to use AES 128 or AES 256 algo. Following are the steps we followed 1. As we have eCOS platform, we just integrated the openssl files (1.0.1g) and added to them to our makefile to build them (only .c and .h files) 2 In our applicatoin we call the openssl functions to above two functions from the openssl. key wrap algorithm to decrupt the session key which is received from the master. AES_set_decrypt_key, AES_unwrap_key MAC algo to generate a mac value for a message (HMAC(), EVP_sha1(), EVP_sha256()) 3. But during the linking stage we are getting the errors as ""undefined reference to a function " Example": openssl/openssl101g/crypto/engine/tb_rand.o(.text.ENGINE_get_default_RAND+0x8): In function `ENGINE_get_default_RAND': undefined reference to `engine_table_select' 4. Not able to figure out if there is any common setting file (to configure openssl ) so that we can enable /disable some features and services. We tried doing the method as your had suggested. But it seems that there is not much effect for the declaration of eCos Request to please let us know what mistake we are making, or we have missed out any configuration. Regards, SSK -- View this message in context: http://openssl.6102.n7.nabble.com/Using-Openssl-for-eCOS-platform-tp67892p67922.html Sent from the OpenSSL - User mailing list archive at Nabble.com.