Best Practices (1) Encryption

Hello,

I am extremely, extremely grateful to you. I see a definite and positive way ahead, and things are coming together.

Two matters on which I would appreciate your input, will understand if you ignore for lack of time, knowledge.

Firstly, I think I should be using encryption on vital fields.

Is there a preferred method of encryption? I know there are various hashes, MD5, and the like. But I don't know the differences.
Is there one you would recommend me to use?

And secondly, I need to be able to read at least some of the sensitive data I will be collecting.
So it's all very well to encrypt say a password field that presumably then becomes unreadable in the database.

But I also need to gather such things as Social Security Numbers, and Bank Account Numbers (so I can pay people).

Am I correct in thinking that if these are encrypted, then I can't read them? Or is there some form of key that is applied on data entry, and that can be reapplied on data read, and that is somehow automatically applied?

I know I can't make myself 100% hack-proof (the Red Cross just got breaced). But are there measures I can take as regards databases, php scripts, and storage that I should engage in, and that other customers of yours use? Or is there, instead, some off-site professional company whose services I can hire to store such info for me for the six or so months I need until my Event is completed.

I do not know who else to ask, and hope you don't mind me benefitting from your experience.

Thank you,
KAB

(Second associated question in a moment)

Most forms of encryption allow decryption with a private key that you can keep separately so as to improve security. So the key may be in your .php pages and the encrypted data in your database. If they just get your database, then they wouldn't be readable, but obviously if they got a hold of the key and knew the type of encryption it would.

I'm not an encryption expert, so I don't regularly read or stay up to date with what is the accepted best option. I think rijndael AES-256 is a pretty common and accepted secure option.