Now that TrueCrypt is gone, how can I share encrypted files between Mac and Windows using a USB flash drive?
Although TrueCrypt can still be used in Mac computer environment, but it is not secure as it may contain unfixed security issues according to an official announcement on truecrypt.sourceforge.net. In this situation, Bitlocker is the best choice.
Bitlocker for Windows
Bitlocker drive encryption is a data protection feature available in Windows Server 2008 R2, Windows Server 2012 and in some editions of Windows Vista/7/8/8.1/10. Having BitLocker integrated with the operating system addresses the threats of data theft or exposure from lost, stolen, or inappropriately decommissioned computers. Data on a lost or stolen computer is vulnerable to unauthorized access, either by running a software-attack tool against it or by transferring the computer's hard disk to a different computer. BitLocker helps mitigate unauthorized data access by enhancing file and system protections. BitLocker also helps render data inaccessible when BitLocker-protected computers are decommissioned or recycled.
Bitlocker for Mac
Although Microsoft only developed and released Bitlocker for Windows version, so Mac OS cannot open Bitlocker encrypted drive, but with the help of M3 Bitlocker Loader for Mac, you can easily open Bitlocker encrypted drive and then read/write Bitlocker encrypted drive in macOS High Sierra 10.13/10.12 (Sierra) and Mac OSX 10.11/10.10/10.9/10.8/10.7 Operating Systems.
Tutorial to share encrypted files between Mac and Windows using a USB flash drive
Step 1: Insert a USB flash drive to a Windows computer where installed Windows 10 Professional/Enterprise, Windows 8/8.1 Professional/Enterprise, Windows 7 Ultimate/Enterprise, Windows Vista Ultimate/Enterprise, Windows Server 2008/2012, only these Windows editions support Bitlocker drive encryption.
Step 2: Format USB flash drive to FAT32/NTFS/exFAT file system
Step 3: Enable Bitlocker drive encryption on this USB flash drive after format completes.
Step 4: Save the password and 48-digit recovery key.
Step 5: Store the files on this Bitlocker encrypted USB flash drive.
Step 6: Safely eject Bitlocker encrypted USB flash drive.
Step 7: Install M3 Bitlocker Loader for Mac on Mac computer.
Step 8: Insert Bitlocker encrypted USB flash drive into the Mac computer where installed M3 Bitlocker Loader for Mac.
Step 9: Open/Mount Bitlocker encrypted USB flash with the help of M3 Bitlocker Loader for Mac on Mac computer and then you can read/write Bitlocker encrypted USB flash drive.