I don't know anything about any cipher or encryption specifically known as "endurance cipher." However, in cryptography, the "endurance" OF a cipher is the amount of time it would take to brute force a ciphered/encrypted string divided by the amount of characters in the plain text...that gives a sort comparison between the ciphers.

This is an uncommonly used comparison, however, because it is relative and changes depending on the exact computer that is being used, and is only an estimation, and is therefore not commonly used. More often a cipher's vulnerability is measured based upon key size or key length, or the mutations in a specific algorithm.

If it is truley a government encryption, then there wouldn't be any info about it online, not because it is quited or censored by the government or anything, but because there would be no use for general information to the public about the encryption. Just out of curiosity, what government is supposedly using it?

I would check your sources...who told you about it? Could he/she have meant they are using a "high endurance cipher/encryption?"

I don't know much about the subject, but it's something to think about.

I presume that the FBI and most US agencies use AES (Advanced encryption standard)

Firstly I would think most Agencies us the encryptions they designed or co designed.

MD5 was mentioned earlier, but its one way. Most data can't be stored like this.

Custom encryptions must be used, with keys. You need your own algorithm or its considerably more insecure. Think of it as using a CMS. Obviously it is much more easy to exploit a CMS because you know its algorithm (code structure in this case) used as its open source.

It is a discussion about whether or not an "Endurance Cipher/Encryption" is used, or for that matter even exists.

I vote no.