Encoding is changing the way data is presented
  - using a public, generally-understood, and (usually) low-overhead method
  - for the purpose of allowing the data to survive intact and easily recoverable after some sort of transfer.

Encryption is changing the way data is presented
  - using a method or a key that is restricted and (as it happens) often computationally intensive
  - for the purpose of shielding the data from some people while making it available to others.

In short, encoding is for preservation, encryption is for obfuscation.

one easy distinction:
• encoding only requires an algorithm
• encryption requires an algorithm and a key
If someone tells you something is encrypted, but they won't tell you where the key comes from, they are selling you snake oil. (e.g. people who think they are encrypting something, but they store the key "hidden" inside the program that reads the data)

dvergin pretty much summed it up, however, I thought take a shot at a practical example--because I think the difference is somewhat more important that "mostly pointless." (Not trying to pick a fight, gryng, just seeing things from a different point of view.)

Encoding (perhaps inappropriately) can be thought of as a communition protocol. It tells clients or transfer agents how to interprete a datastream. When you email me a spreadsheet, for example, my email client uses the encoding to know how to interprete the attached bits into a coherent pattern, a file to be opened later.

As faerloche and arhuman reminded me recently, encoding can be used by any agent receiving that datastream. Thus, if someone intercepts that email message, they can easily open the attached spreadsheet on their own desktops.

Encyption, however, is a privacy device. Only the person with the right key can unlock the encrypted data into a viewable form. Think of it as a wrapper around your data. Encrypted data will be send as an encoded datastream, however, only the person with the right key will be able to makes sense of it.

This is an oversimplification, of course. But I think it illustrates the difference as I understand it.

Also, if you're interested in that book jorg mentioned and want to buy it online, you can give the Monastery a small kickback by clicking here. (I noticed that FatBrain lists it under a different ISBN number.)

--f

Update: I originally answered Desdinova's question by updating this node. After further thought (and reflection on a comment chipmunk made recently), I decided that it was better to reply in a separate post, since that's really a different topic than what I was originally trying to address. To-MAY-to, To-MAH-to. :)

No worries -- I was just giving the definition several crypto-books will say; they claim both words as methods of hiding messages. Colliquially (or perhaps, outside of that community at least), encoding means translating, whereas encrypting means obscuring. The former for ease of communication, the latter to secure communication.

Ciao,
Gryn

How do you make the links so perlmonks gets the kickback? I mention books in some of my posts and would love to link to it like that

For the lurkers: If you like the Monastery and are recommending a book in your node, you may wish to provide a FatBrain link so that Vroom gets a small kickback if someone buys a book through that link. To do this:

1. Locate the book's ISBN number, according to FatBrain. (Use their Search feature to find the most recent edition, as appropriate.)
2. In your node type [ isbn:// ### | Link title ], where ### is the ISBN number.
3. Test your link while Previewing your node. (I usually open it in a new window.)
4. Submit. :)

This also works in the Chatterbox.

Basically you encode if you are taking the data's structure into account (such as translating code words from one to another, or translating alpha-numeric text into alpha-numeric text). You encrypt if you aren't taking the data's structure into account (such as translating bits into bits, or translating alpha-numeric text into alpha-numeric text).

Yeah, I just repeated myself. That's to illustrated the ambivilic nature of the definitions. So basically don't really worry about it. Hope that helps :) .

Ciao,
Gryn

When you encode a piece of data, d, you are applying a function, f, that is reversible by another function, g. Or, in other words, g(f(d)) = d... All the decoding requires is an algorithm.

When encrypting data (I'm going to simplify things) you have a function that takes several parameters and spits out encrypted data. In order to decrypt the data, you must also posess the other data to apply the correct function.

It's a very similar destinction. Code usually refers to a one-to-one relationship between the plaintext and the encoded text: for example, in Morse, a dot is ALWAYS an e, in hex, deadbeef is always 3735928559, in a URL %21 always means a bang (!) and in Caesar type encoding, for the keyword NIGHT an A will always mean F.

In cipher, there is no such correspondance.

Dave

Eight years involved with the nuclear industry have taught me that when nothing can possible go wrong and every avenue has been covered, then is the time to buy a house on the next continent. Terry Pratchett

Here's the primary difference, which is largely functional:

While it is true that all you are essentially doing is exchanging one set of symbols for another, there is a function involved which makes all the difference.

When you encode something the function is directly reversible, such that:

Of course, that's an oversimplification, but you get the idea. You use the same index chart for translating both ways.

encryption involves 2 functions:

While RSA encryption works as you describe, with public and private keys, many other forms of encryption use a single key and a reversible operation for encrypting/decrypting.

In general symmetric ciphers are considered harder to break than asymmetric ones of similar length. They are also often simpler to compute.

actually how the RSA-OAEP work??? i still can't find on the web 1?? especially the OAEP the encode method.. really hard to understand... any 1 can help me?