I do not like D-Bus either, and I do not like JSON either. Some of the problems are the ones mentioned there, and it has many other problems as well (one of these is that its use of Unicode can cause problems, but there is a lot more problems than just that). I do not agree with the solutions mentioned there either, although they do make some improvements, there are also some problems.
A better way would be a different operating system design, although without that, you can still improve it on Linux. I think putting secrets in the message bus is not really the way to do sandboxing properly, and I think there should not be a global message bus (it should be specific to a program; if the program is properly sandboxed it can be limited what it can access, and possibly they can be declared by the use of environment variables, although).
There are also problems with the existing sandboxing systems; e.g. some do not work properly with character sets and might not support such things as: popen, command-line arguments of the program to restrict which files can be read/written, etc.
For security for programs running on the same computer communicating with each other while they are running, cryptographic algorithms are probaly not the way to do it; the operating system should handle the security to prevent programs from seeing and/or tampering with something that it is not supposed to do, so that the communication between programs is prevented unless it is configured to allow it.
For the data format, I might use DER (or SDER for the fields that are not required to be in canonical form, since canonical form does not matter for all fields but for some it might matter).
(The implementation would prevent messages from being sent to or received from whoever it is not supposed to be allowed to do, by checking the permissions and/or by just blocking access, forwarding the messages to proxies that might modify and/or log them, etc; such things can potentially make the system more versatile.)
A better way would be a different operating system design, although without that, you can still improve it on Linux. I think putting secrets in the message bus is not really the way to do sandboxing properly, and I think there should not be a global message bus (it should be specific to a program; if the program is properly sandboxed it can be limited what it can access, and possibly they can be declared by the use of environment variables, although).
There are also problems with the existing sandboxing systems; e.g. some do not work properly with character sets and might not support such things as: popen, command-line arguments of the program to restrict which files can be read/written, etc.
For security for programs running on the same computer communicating with each other while they are running, cryptographic algorithms are probaly not the way to do it; the operating system should handle the security to prevent programs from seeing and/or tampering with something that it is not supposed to do, so that the communication between programs is prevented unless it is configured to allow it.
For the data format, I might use DER (or SDER for the fields that are not required to be in canonical form, since canonical form does not matter for all fields but for some it might matter).
(The implementation would prevent messages from being sent to or received from whoever it is not supposed to be allowed to do, by checking the permissions and/or by just blocking access, forwarding the messages to proxies that might modify and/or log them, etc; such things can potentially make the system more versatile.)