Encrypt string in javascript and C# by the same way to get same results

Question

I'm developping a web app and I need encrypt strings in javascript to compare with strings from the server (.net C#) that are encrypted.

I need to do this by this way, to comprar the encrypted strings in the client with javascript.

How can I encrypt the string in client and server by the same way and get the same encripted string?

Encryption is not idempotent. You may want a hash.

SLaks
– SLaks

2012-06-21 13:46:37 +00:00
Commented Jun 21, 2012 at 13:46 — SLaks
– SLaks, Commented Jun 21, 2012 at 13:46
Hashing isn't idempotent :-/

Rawling
– Rawling

2012-11-30 12:51:40 +00:00
Commented Nov 30, 2012 at 12:51 — Rawling
– Rawling, Commented Nov 30, 2012 at 12:51

David M · Accepted Answer · 2012-06-21 13:49:20Z

1

First thing, since the client-side Javascript needs access to the encryption functionality but not, presumably, the decryption functionality (otherwise why encrypt?) you need to use an asymmetric encryption algorithm. Something like RSA. Alternatively, you could use a cryptographic hash, which is a one-way function. Might help if you gave us some context on what you are trying to achieve, but from the description so far, I suggest you look for implementations of a hash algorithm like one of the SHA-2 family in JavaScript - the System.Cryptography namespace in C# has these already.

If you're implementing some sort of security client-side, beware. If you are, for example, trying to compare a password hash with what's on the server, and you make the comparison on the client side, a malicious user could simply attach a debugger and bypass your logic....

answered Jun 21, 2012 at 13:49

David M

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5 Comments

Callebe Over a year ago

Hi David M. Thenk you for answer.

Callebe Over a year ago

Hi David M. Thenk you for answer. Your Last sentence is exactly what i'm trying to do and i'm aware about the riscs, but my customers want this implementation and they are aware about the riscs too. I'll cache the encripted password for a time to user be able to perform same functionalities offline. Whem the sistems get into online mode, the operations will be validate with server. But i need alert the user if he missis the password. Do you have same link or example code? Thank you.

Callebe Over a year ago

I think that an asymmetric encryption algorithm is the bast implementation for my problem.

David M Over a year ago

I disagree. If what you're passing from the server to the client is a password, then to pass it encrypted in a potentially reversible way, even if asymmetric, is far less desirable than passing a hash of that password. I might add: why are you even storing the passwords? You should be salting and hashing them on the server side as well.

Callebe Over a year ago

Thank you so much. I solved my problem using SHA2. To C# i used clsCrypto To JavaScript i used jsSHA2

Erez Robinson · Accepted Answer · 2012-06-21 13:58:32Z

0

I would use Ajax and use RSA encrpytion from the serverside, that way you use the same code for both.

However if you want genuine javascript RSA encrpytion you can use this library:
Cryptico.js

And for the server side C# code you can check out this site:
C# RSA Example

answered Jun 21, 2012 at 13:58

Erez Robinson

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1 Comment

Callebe Over a year ago

Thank you so much. I solved my problem using SHA2. To C# i used clsCrypto To JavaScript i used jsSHA2

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