The crypto in OpenPGP is actually far from ideal. They combine some arcane block cipher mode with something called mdc ("modification detection code"), which is

The crypto in OpenPGP is actually far from ideal. They combine some arcane block cipher mode with something called mdc ("modification detection code"), which isn't a proper authentication. It's kinda surprising that this hasn't caused more issues (though there were some authentication stripping attacks). It should switch to a proper AEAD mode. Also for RSA it is using PKCS #1 1.5 and SHA-1 is used all over the place. This is all not super serious, I wouldn't be too bothered about it. But it's not a solid crypto design by modern standards.