Thanks for the feedback — you’re right, length alone isn’t enough for a paper backup that lives for years. A single mistyped char keeps the length the same.
We have followed your advice and added a typo check.
Fixed length is now 108 chars Base58 (79 bytes instead of 76), we have added 2 bytes CRC16 in the header checked before any KDF.
Structure: [1 ver | 2 CRC16(salt+iv+ct) | 16 salt | 12 iv | 48 ct] = 79 bytes → 108 chars
Keeps audit simple, but gives confidence before recovery.