[plt-scheme] way to convert from string to digest and back in vyzo/crypto

Anyone (maybe the author) know if there's a way to get a digest method
given its name and get a digest method's name from the digest object?

I'd like to store my password hashes as

digest-type$salt$hash

in my database, and am hoping I can avoid creating a lookup table to
go back and forth from digest types to a string representation
suitable for db viewing.

Thanks,
Todd