Secure browser-based storage on an untrusted server?

Background: I don't know if this is the right newsgroup for this, but
I'm trying to develop a secure online storage application for small
strings, like passwords and PINs. This started as a project for my own
use, because I couldn't find an existing site that I would trust, but I
decided to make it public and open-source for anyone who might be
interested in using it (www.iwhisper.info).

Standard encryption algorithms like AES solve the mathematical
challenges of secure storage (I'm using open source Javascript
implementations of AES and SHA-256 written by others, which pass
standard test vectors).

But that leaves the technical and social challenges of making a public
site trustworthy and secure, without relying overly on trust for the
server and anyone who might be able to access it (myself, my web host,
hackers, ...?).

Is this an appropriate place to discuss these issues? Such as:

1) Javascript is distributed by the server, so an attacker who gained
access to the server could replace the encryption code with code that
gives him total access to user's data.

2) Methods for securely updating data or removing it from the system,
which require the user's private key without transmitting that key to
the server.

3) Methods for securely and conveniently storing the user's private key
on the client computer (cookies?).

.

Relevant Pages

  • Re: write with cURL
    ... It takes time to set up an account for you, process the billing, etc. ... Sorry, my servers are secure. ... Nothing you have told me shows me you know how to lock down a server so that it is secure - other than to use the server's file security. ...
    (alt.php)
  • Re: NT4 -> Win2K3 question
    ... disable SMB signing for the Workstation or Server service on a domain ... Get Secure! ... The File Replication Service Event log test ... controller to the following destination domain ...
    (microsoft.public.windows.server.migration)
  • [OT] Re: RSA implementation, please comment.
    ... on a separate server is actually a very good idea, ... This web front uses a well defined and secure ... Don't store the private key on the server. ... Every client gets a smartcard for the decryption (or a HSM, ...
    (comp.lang.perl.misc)
  • Re: private key generation on-the-fly
    ... way encryption of csr be enough? ... and on the fly private key ... However, it isn't any more secure than what's already in use by banks, medical professionals and others every day - and probably still less secure. ... you seem to be concerned about the data being intercepted between the client and the server. ...
    (comp.lang.php)
  • Re: Word 2007 Missing User Level Securitty - ARRRGGGGHHHH What were they thinking?
    ... File servers aren't secure? ... Access predates Windows security, ... database system has never been updated or kept current. ... the OS-based database server product, ...
    (microsoft.public.access.security)
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