so, a HD seed

i still think you should use a crc32 check, and hex, to make the decoder simple as possible... base32 and base64 are shit in this respect

you could make a simpified 256 word dictionary mnemonic key scheme too, that would be 32 words, plus another 4 for your CRC check or 36 words, they could all be precisely 4 letters long to make storage neat