Why would one need to encode an MD5 hash string? Is it unsafe to display unencoded?



  • I was reading this article which talks about a design to shorten URLs, and in the design section, it says that the given URL can be hashed using a hashing algorithm such as MD5, and then be encoded for display purposes using base64 or similar encoding.

    I am confused so as to why would we need to encode a hashed string. Is it not safe to display an MD5 hash, or is there any other benefit? Can anyone shed some light on this? I tried searching online, and a lot of pages talk about encryption, etc but not about the above scenario.



  • Hash functions output binary data, usually as a byte array. This cannot be displayed correctly, therefore, you need encoding.

    Transmitting binary data can create problems, especially in protocols that are designed to deal with textual data. To avoid it altogether, we don't transmit binary data. Many of the programming errors related to encryption on Stack Overflow are due to sending binary data over text-based protocols. Most of the time this works, but occasionally it fails and the coders wonder about the problem. The binary data corrupts the network protocol.

    Therefore hex, base64, or similar encodings are necessary to mitigate this. Base64 is not totally URL safe and one can make it URL safe with a little work.

    In another way, character encodings are reversible and don't require encryption keys. This has nothing to do with security; it is about visibility and interoperability.



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