base32 with included forward error correction (FEC)?

Question

I am trying to find (or pipe together) a way to encrypt text so that the output is base32 encoded and protected by forward error correction against lost characters.

Having some some base32 output like NBSWY3DPEB3W64TMMQXAU=== I would like to transmit it, and even if NBS_Y3D_EB3W_TMMQXAU=== is received ("_" = missing character) or NISWY3DZEB3W6WTMMQXQU=== is received (wrong characters) I'd like a correct de-base32 that I can then pipe to my decryption.

In detail:

This is for a purely hypothetical situation in which I must transmit an encoded message via telephone, shortwave or any other spoken text or morse channel. I.e. nothing "digital" that can handle >5 bit text. On the other side, a human will pick up and transcribe the message and then feed it into a computer for decryption.

I've tried openssl enc -e -aes256 -k "12345" -nosalt -pbkdf2|base32 (-nosalt just for human eyed verification of repeated attempts), but that doesn't have any FEC.

Piping the openssl-output into some FECing tool (redupe, fecsum, par2) and then base32ing the result yields unsuable FEC as base32 doesn't like any characters to be missing.

The output of the FECing tools that I know produce no base32 output. And here I stand, basically looking for a base32 implementation that is hardened by an included FEC mechanism (LDPC, Hamming codes etc.).

Any ideas?

• Joop Eggen: That looks like you have to do FEC yourself on 5 bits words. Are you sure this is not some programming task?
• Christian: @JoopEggen I'm 47 and working in a completely different field - no, it is not ;)
• Joop Eggen: Sorry, but it is that if a "digit" is dropped entirely or some bits altered (hamming say % instead of E, 2 bits; or §/ G) then 5 bits are concerned, so it does look to me very specific programming is needed. Upvoted your question