Re: Should Ada runtime provide special primitives for cryptography?

[Florian Weimer <fw@deneb.enyo.de>]

* Natasha Kerensikova:

> However, when actually implementing cryptographic stuff, cleverness from
> compiler and optimizer are often enemies. For example, overwriting a
> buffer with zeroes might be optimized out when the buffer is not
> accessed again.

Pragma Inspection_Point covers this.

> I believe it would not be difficult for a compiler vendor to provide, as
> part of the runtime, a zeroing procedure guaranteed to not be optimized
> away, a (generic) array comparison guaranteed to execute in a constant
> number of operations and/or branches, etc. And such subprograms would be
> difficult to write externally, and the guarantees difficult to make
> without tight compiler integration.

The compiler cannot guarantee constant-time execution, that's a
property that emerges from the combination of the object code and the
execution environment (or not).