undefined function hash_hmac()

Content

Hi,

I am trying to call a webservice using curl in php. I am supposed to pass encrypted data and i tried using hash_hmac() function. While running the script i am getting the following fatal error 

"Fatal error: Call to undefined function hash_hmac() "  

php version that i use is 5.3.2

Can any one help me with this?

Thanks in advance,

Shilpa