Iteration exponent overflow

[onvej-sl]

The implementation doesn't check whether the iteration exponent used to generate shares fits within 4 bits. This may result in generating shares that cannot be recovered by this implementation.

Steps to reproduce:

shamir create 1of1 -E 16
Using master secret: 4da64d0fae60d682e6846743625457e1
Group 1 of 1 - 1 of 1 shares required:
patent flea academic academic bundle tricycle analysis leaves finger density receiver chew inform glasses elephant unknown birthday large group floral
shamir recover
Enter a recovery share: patent flea academic academic bundle tricycle analysis leaves finger density receiver chew inform glasses elephant unknown birthday large group floral
ERROR: Invalid mnemonic checksum for "patent flea academic academic ...".