User Caching

You would use these functions. https://developer.khoros.com/khoroscommunitydevdocs/reference/usercache-1

Example: 

<#assign key = "digest"+user.id />
<#assign digest = usercache.get(key,"") />
<#if digest == "">
    <#assign val = utils.digest.hmac("12345678901234567890123456789012", "This is my message") />
    ${usercache.put(key,val)}
</#if>