How can an amateur introduce a cryptographic algorithm? I have a new cipher, and I want to get it properly vetted, but I don't have a strong way to prove its security properties.  I'm an amateur without ties to a strong cryptographer/university.  I have attempted a few indistinguishability proofs, but these are "back of the napkin" proofs and are likely not rigorous.  (I have colleagues that have done cryptanalysis on it, but they are not theorem types.)

As a result, I feel that I don't stand a chance of getting it published without a proof of security, but I feel that I can't find someone to help without it being published.

How can I find someone willing to join on and help write a compelling proof, and generally help write a compelling paper, (or identify a weakness that prevents me from doing something stupid with the cipher)?

Given that I have done these things:


Review previous ciphers, find they're not what you want, invent new cipher
Internally analyze it (plots, prototype code, etc.)
Socialize it to cryptanalyst peers, get tentative green light (rather, absence of red light - no new findings in a while)


Is this a reasonable path going forward:


Brief it at an IACR rump session
Have follow-on discussions at conference, express my need, find someone that way
Submit as a work-in-progress in lower tier, but bonafide crypto conference
Submit as a journal article


Is a rump session a good way to go to find interested math types, and/or as a first step to announcing the idea?  Are there other alternatives, such as quarterly meetings of some group that might be willing to hear the idea?

Similarly, is there a good "starter conference" for crypto open to new ideas that might lack the mathematical rigor?

In contrast to this thread, How to publish a cipher (concept), the main answer suggests that formalisms are a prerequisite to publishing: "If you submit a cipher, one would expect at least a formal analysis of why you think this is a good idea."  My question is what if you don't have that ability - how do you find someone that can help with that?  The rest of the answers on the thread went into how to make it into a bachelor's thesis.  

In additional defense of this thread, there are many great suggestions that don't appear on that other post.  While I'm biased - but have nothing to gain - these threads are unique.  I'm okay with marking as duplicate as long as somehow you can merge the useful answers below into the other question.
First, if it's a secret-key cipher, then you'll never find any proof of security—at best you'll, exhaust the standard cryptanalysis techniques and exhaust the brilliant ideas of the brilliant cryptanalysts.  If it's a public-key cryptosystem, then at best you can prove reduction to a widely understood uniformly hard problem.  If you're not already familiar with these facts, you won't get the attention of serious cryptanalysts.

Second, you need to convincingly demonstrate (a) that you understand the standard cryptanalysis techniques, and (b) that it does not fall to them.  Cryptanalysts don't want to waste time doing your homework.  If you haven't already done your homework, you won't get the attention of serious cryptanalysts.

There's no good textbook of which I'm aware on this subject, but you might start with


  Bruce Schneier, ‘Self-Study Course in Block Cipher Cryptanalysis’, Cryptologia, 24(1), January 2000, pp. 18–34.
  https://www.schneier.com/academic/archives/2000/01/self-study_course_in.html


Third, if you want this to be anything more than an amusing intellectual exercise for bored cryptanalysts whose attention you've gotten, your cryptosystem has to fill a niche that nothing else does.  Is it faster or lower-energy on some significant platform than every other cipher providing comparable security?  Does it fill a specific need that no other cipher does, like a weird block size that is important for some particular reason?

For example, Gimli is a sponge with a much smaller state than Keccak-f1600, conveniently fitting in registers on more platforms, out of which one can build all manner of secret-key crypto gizmos.  (Gimli is a very new design, with some preliminary theoretical cryptanalysis.)

If you propose a general-purpose stream cipher that's not faster than software ChaCha or hardware AES-CTR, or a general-purpose collision-resistant hash function that's not faster than software BLAKE2b or hardware SHA-3, you won't get the attention of serious cryptanalysts who aren't either just bored or hoping their novel pet cryptanalysis techniques that failed to break the aforementioned ones might break something.

This applies even to designs that already have been published: Maybe RIPEMD160 resists collisions better than SHA-1 does, but it's not worth the time of most cryptanalysts to study it.  Maybe CAST6 is a better 128-bit block cipher than AES, but it's not worth the time of most cryptanalysts to study it.

Finally, if you want to get the attention of cryptanalysts, don't start with your cipher—start by showing that you are a competent cryptanlyst by using novel techniques to break crypto!  Best if you can break existing cryptosystems that were previously unbroken, or break them worse than the best published attacks.  This may be easier if you study cryptosystems that have received relatively little attention, including your own.

If you have a write-up demonstrating all of this—either a description of a novel cipher with evidence of resistance to standard cryptanalytic techniques and a reason to be interesting, or a novel cryptanalytic attack on an existing cipher—then a first step would be to submit it to the IACR cryptology eprint archive.  That won't impart the kind of serious review that, e.g., the AES and SHA-3 competitions did, of course, but it may catch the notice of some cryptologists and will be easier to show to someone whose review you are seeking, and if you do get the attention of a serious academic cryptologist they will likely have followup suggestions for publication venues.