I did some tests and it turns out that the culprit isn't the crypt command, but when its run with chunking.
config is below:
This contains 100 char cyrpt and 3 char crypt.
[local]
type = local
[crpt100-local]
type = crypt
remote = local:
filename_encryption = standard
directory_name_encryption = true
password = xxx100
password2 = xxx100
[chnk-crpt100-local]
type = chunker
remote = crpt100-local:
chunk_size = 1M
hash_type = md5
[crpt3pw-local]
type = crypt
remote = local:
filename_encryption = standard
directory_name_encryption = true
password = xxx3
password2 = xxx3
[chnk-crpt3pw-local]
type = chunker
remote = crpt3pw-local:
chunk_size = 1M
hash_type = md5
The source leaf file is:
357A75YK6EO4IO3E3EY434VXHBHQJEEJG7HOBP3UZSY7ZU2JRXZX37X4YIFPNPKHB6TPVKNJMZW5NDMJ2266P47QJVFFAIXB6JC4ZB5F5LLS6VQ=
This is 112 char long.
when it goes through the 100 char crypt WITHOUT the chunker, there are no errors as below:
2019/11/04 22:54:27 INFO : d/33/BZTFK2NX4C4OQVFZZ7CQOKY2HCUVIR/357A75YK6EO4IO3E3EY434VXHBHQJEEJG7HOBP3UZSY7ZU2JRXZX37X4YIFPNPKHB6TPVKNJMZW5NDMJ2266P47QJVFFAIXB6JC4ZB5F5LLS6VQ=: Copied (new)
When the same source file goes through the 3 char crypt WITH chunker then we get the LONG filenames that make the errors as below
2019/11/04 22:56:36 ERROR : d/33/BZTFK2NX4C4OQVFZZ7CQOKY2HCUVIR/357A75YK6EO4IO3E3EY434VXHBHQJEEJG7HOBP3UZSY7ZU2JRXZX37X4YIFPNPKHB6TPVKNJMZW5NDMJ2266P47QJVFFAIXB6JC4ZB5F5LLS6VQ=: Failed to copy: open /mnt/data/sync/test-data-cyrptom/mrqupgirc9apqh4g34durgucnc/v16cb0h0k313v72o884aubs2nk/4rf2tlgbh9188jkssacnc3qfb8/bl481m1isan9v7c805riiakrv32honddfikc3rbs6gl27g0a67k0/mi46msgd6l3u161tukc1na4p9a1euih56d8toghq9rih1v92450efmbpnja1co0786s3gs5ngqvhpqe3tflikmo05bsq5n6egqunmcm84dsat0f112j3g63874eihkbcnfgvqkcogvhalnr531gu2ltos9p3nhada8df8h0356lmnm2otbnd74g37d95qhf8h78i0v325qcv5u9der1u88ve6hlk3r60ajnvqdk7eccbfonriqhdjllaq3ch4h3p: file name too long
The resulting encrypted leaf file is 256 char long. Other files are longer.
The commands used for the 3 pw char with chunker and crypt.
2019/11/04 22:56:28 DEBUG : rclone: Version "v1.50.0-016-g7bf05631-beta" starting with parameters ["rclone" "sync" "/mnt/data/sync/data-cryptom/" "chnk-crpt50-local:50/" "--fast-list" "-P" "-vv" "--log-file" "50.log"]
and for the 100 pw crypt without chunker =
2019/11/04 22:54:23 DEBUG : rclone: Version "v1.50.0-016-g7bf05631-beta" starting with parameters ["rclone" "sync" "/mnt/data/sync/data-cryptom/" "crpt100-local:100/" "-vv" "-P" "--log-file" "100.log"]
Maybe its the additional information that the chunker adds to filename, although it still shouldn't be that long?