i guess moral of the story, security can not be achieved by software alone. Hardware support is a must.
...and then it still cannot be achieved in the ideal, asymptotic sense of "the security".
Largely depends on context, AoV.
Technically, practically or economically?
one can always use brute force technically but considering lifespan of a cracker's age etc., and time to crack using brute force, it can be technically insecure but practically secure.
if considering cost of effort, money involved is not worth the benefit, then economically it is secure.
btw, I am just repeating the author's words of very good crypto book i used to read.