Answer by DrM for Why is it wrong to *implement* myself a known, published, widely believed to be secure crypto algorithm?

Very simply, older more widely used encryption software, has been subjected to more testing (friendly and unfriendly) and more analysis.

Moreover, the history of encryption is littered with broken software, some of which was authored by eminent expert cryptographers.

So, the codes that you can have the most confidence in, are very often, the codes that have been around for a while.