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Cannot import key: "Key file is not a recognized format or is empty" (Robo-FTP 3.5 and earlier)

Solution #1

Upgrade to a new version of Robo-FTP. Robo-FTP version 3.6 and later uses an implementation of OpenPGP which supports the IDEA encryption algorithm.

Solution #2

If the key is of type RSA legacy, the cipher for that key may be of type IDEA. IDEA is patented by the PGP Corp. and is not officially supported by Robo-FTP 3.5 and earlier.

If you get an error while using the Robo-FTP Configurator to import the key, then you need to check if the key is an RSA Legacy key with the IDEA cipher, as Robo-FTP does not currently support this key type.

You can check if the type is RSA Legacy / IDEA cipher by executing a couple Robo-FTP commands.

Go to the windows start menu, select All Programs, and then the Robo-FTP program group. Then select "Robo-FTP." This will open the main Robo-FTP console window. The cursor is already blinking in the main input screen; you'll need to enter the following commands there:

1) First, if the key is ASCII armored, you will need to de-armor it. Key files ending with ".asc" are ascii armored, while keys with different file extensions are not. Use this command to remove the ascii armor:

DOSCMD 'gpg.exe --homedir . --yes --dearmor "rsa legacy.asc"'

2) Then, run the following command to generate an output file with information on the key file.

DOSCMD 'gpg.exe --homedir . --yes -v --verbose --import "rsa legacy.gpg" >> "import.log"'

the output file ("import.log") will have something like the following:

:public key packet:
version 3, algo 1, created 830173876, expires 0
pkey[0]:  [1024 bits]
pkey[1]: [5 bits]

If you see "version 3, algo 1" then the key is an RSA Legacy key, and is not supported by Robo-FTP.

In more detail: the way to recognize an RSA Legacy key is by noticing the version and algo. Algo 1 is RSA and version 3 is the Legacy key type (which is not supported), while newer RSA keys (which are supported) will output version 4.

For more information, use the keyword "IDEA" to search this Knowledge Base.

Article last updated: 2021-03-11

Tags: PGP Key, Robo-FTP, IDEA