I'm looking to design a system that allows a user of a crypto-coin such as Bitcoin to both have an online wallet and to be able to send and receive encrypted emails in the same system.
The relevant portion concerning Bitcoin is that for a user's address, such
31uEbMgunupShBVTewXjtqbBv5MndwfXhb, is a hash of the user's public key. The keypair is a ECDSA public-private key pair.
If I am a user, could I use this key pair for both Bitcoin transactions and for sending and receiving encrypted emails? Besides the given that using a key pair for both things may be unwise, are there any additional pitfalls I should be aware of?
Edit: I'm looking to use a system such as OpenPGP, not S/MIME. To be more specific, I'm attempting to see if it's possible to use the key pair generated by a Bitcoin or Litecoin derivative, which is a ECDSA key pair, in an email like system so that users of this email system can use and exchange key pairs with other, non-system users such as those using GnuPG.