The article feels too technical for a non-technical person. Can anyone please give a brief "Explain me like I am 5". Thanks.
In 1999, Judge voted that, no, encryption code was "scientific expression" and thus protected by the freedoms granted by First Amendment.
There was a fair bit more back-and-forth including shifting positions by the government under various administrations, but in effect this is the case that opened the gates to better public encryption.
https://en.wikipedia.org/wiki/Curve25519
I saw him give a really awesome talk about the process of finding Curve25519 around the time he published it, and I think the story is a lot more interesting than people realize.
Curve25519's group of points over the whole curve is not of prime order. By Lagrange, the subgroups are the prime factorization of the group order. Luckily we do have a large prime order subgroup, but we also have a subgroup of order 8 and consequently of order 4 and 2 also. If you by chance decode a point into one of these groups, scalar multiplication has a high chance of hitting the identity point. In Diffie Hellman, this isn't a problem: we call it "non contributory behaviour".
If however you care about each party making a contribution and group properties, you end up having to check group membership anyway. Not having to do that is one of the main selling points of Curve25519.
Looking through the SafeCurves criteria, there are now complete addition law for prime-order weierstrass curves, negating another safecurves benefit. Since the NIST curves form a prime order group, they don't have the same subgroup problem (all Montgomery curves, by contrast, have a subgroup of order at least 4).
We owe the "fix" to this to Mike Hamburg, effectively, who came up with a mapping to and from a Jacobi Quartic form that allows you to encode and decode directly into the prime order subgroup. This is Decaf, one of the contributions of his Ed448-Goldilocks paper, and was applied to Curve25519 under the name Ristretto.
We can go further if you like. There's extensive literature on appropriate choices of pairing friendly curves, and I'm not aware of any DJB contributions here. There are also faster curves at the 128-bit security level for Diffie Hellman, i.e. FourQ, which uses the GLV decomposition and Q-curves. ---
While DJB has made some very notable contributions and helped push the state of the art along, he's not the only contributor to the field by a very long way. At the very least, we should also mention Peter Montgomery and Harold Edwards, but these are by no means the only names.
An awful lot of things are built on NaCl, which is probably what djb is most famous for.
Before DJB became famous in encryption circles, he was famous for writing qmail (an SMTP mail server that was a more secure and simpler alternative to the ubiquitous sendmail).
> His software converted a one-way “hash function” (one that takes an input string of arbitrary length and compresses it into a finite, usually shorter, string; the function has many uses in cryptography) into a private-key encryption system (one that can be decoded only by whoever holds the private “key,” or pass code). The functionality of the software depended on two people’s having exchanged their private keys.
I get what you're saying, that would typically mean encrypt with private key, and decryption with public key, like how signature algorithms work, but still, there is no cryptosystem that makes it okay to start exchanging your private keys with random parties you're communicating with, by the very definition of "private key".
In public-key encryption, they share public keys.