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strings from DynamoDB that were originally byte arrays have funky values

Now I'm not sure if this is something I'm doing wrong, or something thats happening in DynamoDB..
Basically, Im building a simple registration/login system for my project, saving the userdata/password in a DynamoDB instance with the password hashed using RIPEMD160, and salted as well using C#'s RNGCryptoServiceProvider().
Registration seems to work perfectly fine. the issue is upon login, no matter what, the passwords dont match up, and I think its because I'm getting some funky characters back when pulling the hash/salt back from DynamoDB. First off, both the hash and the salt are byte arrays of length 20, and converted to strings before saved in the database.
These examples are copy/pasted from the dynamo web interface
Example Hash: ">�Bb.ŧ�E���d��Ʀ"
Example Salt: "`���!�!�Hb�m�}e�"
When they're coming back and I debug into the function that pulls back the data from dynamo, both strings have different characters (VS2010 Debugger):
Returned Hash: "u001B>�Bb.ŧ�E��u0003�d�u001C�Ʀ"
Returned Salt: "`���!u000B�!�Hb�u001Dmu0012�u0001}e�"
Seems these u001B, u000B, u001D, u0012, u0003, u001C, and u0001 are sneaking into the returned data, and I'm not entirely sure whats going on?

You shouldn't be trying to convert opaque binary data into a string in this way in the first place. They're not text so don't treat them that way. You're just begging to lose information that way.
Use Convert.ToBase64String(data) instead of Encoding.GetString before putting the data into the database. When you get it out again, use Convert.FromBase64String to retrieve the original binary data.
Alternatively, don't store the data in a text field to start with - use a database field type which is meant to store binary data...

Encoding two values in a short URL token

I am working on a short URL app, where the token must identify 2 values: the link ID and the user ID. Ideally this token should be short.
For example, considering the URL http://sho.rt/15qq6, the token "15qq6" must identify the link and user ID.
I guess one option is to insert both values in a table and use the auto-generated ID as a token, but I would rather not. I would prefer a solution involving encryption.
How could I use the .NET encryption classes for such purpose, if possible? Many thanks for your help.

I'm not clear on how short you want your code. I posted some code online to encrypt any number of query arguments.
The result could be shortened by base64-encoding the result. That might still not be short enough for you though. (Note that I didn't base64-encode it because I had some concerns about base64 encoding is case-sensitive.)
Another approach would be to come up with a code that consists of an ID into your database and some sort of checksum. If the user tries modifying the ID, you could detect this. However, this approach may not be that secure since it might not be that hard to figure out how to create your own checksums.

Short answer is "You can't", at least, not easily.
Encryption typically doesn't change the length of the data being encrypted. So if you take the URL and UserId that you want to encode and encrypt them you'll end up with a token that's the same total length.
You could try compressing the data before encryption, but there's not a lot of redundancy in a single URL, and this won't buy you much.
You culd hash the data to give you a shorter result, but there's no way to reverse this process to get your URL and userId back.
If it's a short token you need then the only real option I can think of is a lookup table on the server, using the token as the key.

I don't think you understand exactly how Encryption works.
Encryption is just a technique for making it difficult to decode the response, without knowing the original encryption key.
The encrypted data is at least as long as the original data, if not larger.
There is no viable way of encoding a URL into a smaller amount of data, that's still valid in a URL.
Use a database for this, that's what they're for.
Edit: D'oh, Andrew beat me to it with a better response after editing.

You could use something like the RNGCryptoServiceProvider to generate a unique set of characters. Use a few constants strings holding a range of characters like "a" to "z", "A" to "Z", and "1" to "9". Save the randomly mixed case alphanumeric string with the original URL and UserID.

Generate random token and save link and user id in db for this token. It is security enough.

If you don't need encryption, than simple combination of Convert.ToBase64String and BitConverter.GetBytes will give you reasonable string. Note that Base64 uses some non-url cahnracters, so consider replacing them in result WikiPedia Base64, or using Base32 encoding.
int first =1234;
int second =789;
var encoded = Convert.ToBase64String(
BitConverter.GetBytes (((ulong)first<<32)+(ulong)second));

Asp.net C# Encryption/Decryption on Client and server Side

Sir,
I have the jquery solution to encryption on the client side but it create "MD5" only.
I want Salted Md5 Encryption on the Clientside
and Decrypt it at the Server Side in Asp.net 4.0 and C#
My Code for encryption are as follows:
<script type="text/javascript">
function chn() {
var a = document.getElementById('txt1');
var b = document.getElementById('txt2');
var c = a.value; var d = $.md5(c);
b.value = (d);
}
</script>
I want that encryption must be change on every attempt..
Example : first time encryption of abc is xyz
and again if I will try with that name "Abc" then it should create another Encryption
and check on server Side.
Please Help me out

MD5 is a hash, not an encryption mechanism. Hashes are by their very nature lossy, and multiple inputs can (and by virtue of the pigeonhole principle absolutely will) produce the same outputs.
Running MD5 works like counting the number of vowels in a word. If I tell you that a word has 4 vowels in it, and ask you to tell me what the original word was, you simply don't have enough information to give me the the correct answer. You may be able to find some word that has 4 vowels in it, but you won't know whether the word you found was my word. Maybe it is, maybe it isn't. It's mathematically impossible for you to tell.
MD5 works the same way. You're throwing away tons of information, possible gigabytes or terabytes of information, and producing instead a single 16-byte summary.
It is, by intention, an inherently one-way process.

MD5 cant be decrypted. It is a one way hash. Beside I find that anything that could be decrypted on the other end is insecure, in the case it is intercepted. Always design and code to ensure that you can validate a salt and not decrypt it :)

Initialization vector - DES/triple-des algorithm

In order to generate the encrypted data we would need to define a Key that should suffice generating the data. But in .net DESCryptoServiceProvider requires Key and Intialisation Vector to generate the encrypted data. In this regard, I would like to know the importance & the benefit gained by defining this initialisation vector field. Is this mandatory while encryption using DES algorithm.
Pls share your thoughts on the same.
Regards,
Balu

If a key is used to encrypt multiple items that happen to be the same (or start out the same) without an initialization vector, you'll get the same ciphertext output, which is a pretty big problem.
Using a unique initialization vector for each item that's encrypted solves that problem.
See http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Initialization_vector_.28IV.29 for a bit more detail.

Iterative / Additive MD5

I need to generate a checksum over a dictionary. Keys and Values.
Is there any simple way to accomplish this in an iterative way.
foreach(var item in dic.Keys)
checksum += checksum(dic[item]) + checksum(item);
In this case, keys and values could be converted to strings, concatinated and then a single checksum applied over these but is there a better way?
Ideally MD5 but other options could work. Using this to validate data that is passed over a couple of storage methods. The checksum is then encrypted along with some other information (using AES) so I am not horribly worried about an ideal, unbreakable checksum.

Generating a signature is pretty much the same process all over: create a MD5 hash object, then you digest all the bytes of interest, then you extract the hash value. The important thing is that you and the verifier agree on the bytes to hash and on the order they are hashed.
In C# you can achieve this by calling HashAlgorithm.TransformBlock repeatedly, and then finally calling HashAlgorithm.TransformFinalBlock. This is automated by using a CryptoStream with a HashTransform (MD5 implements ICryptoTransform) and then simply writing your dictionary into the crypto stream.
As aside note, countless protocols and crypto schemes that digest a hash and encrypt it were humiliated in the wild. I would suggest taking the beaten path and use well established industry standards::
Use a HMAC, see HMACMD5
Use an RSA signature (ie. private key encryption of an MD5 hash), and save your self from all key provisioning and master secret exchange problems, see RSACryptoServiceProvider.SignHash

Answered my own question I think....
GetHashCode() on each item. Add them in an unchecked {} environment. Too simple.

You should not be writing any new code relying on MD5. It's deprecated, and for some extremely solid reasons. You should look at SHA-256, or at the very least SHA-1, instead
And you should take Remus' advice. Cryptography + hashes = digital signatures. Pull something down off a shelf (just not XML-Security, please!), learn it, use it, and get on to other interesting parts of your project.