Quoting fusefrontend_reverse/node_helpers.go :
// File names are padded to 16-byte multiples, encrypted and
// base64-encoded. We can encode at most 176 bytes to stay below the 255
// bytes limit:
// * base64(176 bytes) = 235 bytes
// * base64(192 bytes) = 256 bytes (over 255!)
// But the PKCS#7 padding is at least one byte. This means we can only use
// 175 bytes for the file name.
Noticed by @bailey27 at https://github.com/rfjakob/gocryptfs/issues/499#issuecomment-955790427