You can use 7zip to archive, compress, and AES-256 encrypt.
You can also use GnuPG or openssl to encrypt a file or a disk image.
Lately I took a look at actual filesystems for cross-platform use. I didn't find a great one, but depending on which OS you want to burden with an extra driver, pretty good ones include exFAT, NTFS, and UDF specifically version 2.01. Like you, I am curious whether better answers are available.
You can also use GnuPG or openssl to encrypt a file or a disk image.
Lately I took a look at actual filesystems for cross-platform use. I didn't find a great one, but depending on which OS you want to burden with an extra driver, pretty good ones include exFAT, NTFS, and UDF specifically version 2.01. Like you, I am curious whether better answers are available.