Is there any forum or website on the internet except reddit subs where you can send in your hand cipher to get it analyzed?
$\begingroup$ I've migrated here to meta as asking for references is off topic; asking about what's good is opinionated - another reason for being off topic - as well. Maybe somebody here is willing to answer though. $\endgroup$– Maarten Bodewes ModFeb 24, 2019 at 15:25
$\begingroup$ Could you clarify by "get it analyzed", did you mean to just get the hand cipher solved? Or to analyze deeper like the strength and the weakness? $\endgroup$– Andrew T.Feb 24, 2019 at 18:25
$\begingroup$ I mean the latter $\endgroup$– user65597Feb 24, 2019 at 18:26
$\begingroup$ Is reddit's /r/codes not good enough? And for attempts at more serious ciphers, there is a dedicated thread in /r/crypto for it $\endgroup$– NatanaelFeb 24, 2019 at 20:05
$\begingroup$ The thing is I have already posted the cipher in r /codes and took their advices I even had a private conversation with an user who was really eager to study my cipher but unfortunately in the end he admitted that he (quote) :"doesn't have that kind of advanced knowledge" $\endgroup$– user65597Feb 24, 2019 at 20:35
$\begingroup$ Do you think I could post the cipher in r/crypto without getting the post deleted? $\endgroup$– user65597Feb 24, 2019 at 21:06
$\begingroup$ @user65597 In the dedicated review thread, yes, but not outside it (I'm a moderator there, so I should know). reddit.com/r/crypto/comments/9kk5gl $\endgroup$– NatanaelFeb 24, 2019 at 22:25
You can ask such questions on PuzzleSO. They have a cipher tag which has currently 1186 questions.
The tag has the following definition:
A cipher is a simple method of modifying messages to make them unreadable, but still possible to recover. Common ciphers are Caesar, Vigenere, Atbash, and several types of substitution cipher. Other ciphers include polynomial ciphers such as Playfair, Foursquare, etc
$\begingroup$ Do you know any alternatives $\endgroup$ Feb 24, 2019 at 19:54
The first solution
I suspect that this is an example of an XY problem.
What you want is analysis of your cipher. The pre-supposed solution is to find someone else to do that analysis.
I propose that you already have someone to do that analysis: You!
Try to find a pre-existing design that is similar to yours that has attacks against it. Or find a course on cryptanalysis of (classical) ciphers. Or just sit down and think about what information you have and how you can use it.
Until you are already familiar with all of the standard and/or generic approaches to attacks, then asking for others to do the analysis is counter-productive towards your own education (which is what I presume designing classical ciphers is for) and will not improve your ability to construct superior designs.
Asking questions on crypto.stackexchange
If you are really stuck, and you can make your question narrow and precise, then asking for help on the main site is fine.
However, it is important to note that posting your design and asking for someone to break it is thoroughly frowned upon, and such questions will be closed. We require that you list what you have tried, and where you are stuck.
You would need to have a concise description of the relevant part of the algorithm that you have a question about. It should not be a code snippet - we are more of a math site than a programming site, so explain the design in mathematical terms as best as you can. Try learning to use TeX, it will help the reception of your question significantly.
If in doubt, look for old questions about algorithm design and classical ciphers that were not closed, that received positive votes, and that received answers. Then use such questions as a template to ask your own.
Ask in chat
Once you have sufficient (20) reputation points on the main site, then you can use The Side Channel, which is the chat room for cryptography.stackexchange. You can ask about anything you want there - however, you are not guaranteed an answer.
The pre-supposed solution
I leave this to others to find recommendations here - I don't know of any.
Until you have a design that is noteworthy in some sense (very fast, provably secure, existing analysis, etc) then few knowledgeable people will be interested/willing to work on it.
$\begingroup$ "Until you have a design that is noteworthy in some sense (very fast, provably secure, existing analysis, etc) then few knowledgeable people will be interested/willing to work on it." $\endgroup$ Feb 24, 2019 at 16:42
$\begingroup$ Isn t that rather subjective? $\endgroup$ Feb 24, 2019 at 16:43
1$\begingroup$ @user65597 I'm not sure it's possible to objectively (e.g. quantitatively) remark on the probability that experts in general will/will not be interested in examining a given design. So in that sense any such commentary must be subjective. $\endgroup$ Feb 24, 2019 at 16:56
$\begingroup$ That is right of course $\endgroup$ Feb 24, 2019 at 16:58