If it's a "trusted" source, as in a popular one, such as a certain link from a certain girl that is fit, yes.
Otherwise another option I've done for a while was buying cheap keys from greymarket type resellers, though for those I only did them from AAA publishers never putting their games on sale and on a second account (idea being you minimize risk and if something did turn out to be a stolen key, which was a problem for a while on those kinds of sites, a chargeback isn't going to hurt a AAA publisher as much as an honest small published in house indie dev team).