Are there any "real world" implementations of secret-sharing encryption schemes?

There are at least two free implementations that are part of Ubuntu linux and implement Shamir's secret splitting and combining:

• gfshare: Ubuntu Manpage: gfshare - explanation of Shamir Secret Sharing in gf(2**8) provides both tools for secret sharing (gfsplit and gfcombine) which can split an arbitrary file into shares, as well as a library for use by developers.

• The "ssss" package provides the ssss-split program which prompts you for a pass phrase which can't be longer than 128 characters, to split up into a set of phrases to share. Then the ssss-combine program prompts for enough of the shared phrases and prints out the secret.

gfshare directly works with files, while ssss would be used to split up a pass phrase which can then be used with gpg or openssl or another encryption utility. So gfshare would seem simpler for your use case.

I want to say that the commercial PGP product has had this feature for at least 10 years. It currently has this feature now:

http://www.pgpi.org/doc/pgpintro/#p24 and http://www.symantec.com/business/support/index?page=content&id=HOWTO41916

Here's a Shamir's Secret Sharing library I put together in Python: https://github.com/rxl/secret-sharing.

It's really simple to split secrets:

>>> from secretsharing import SecretSharer
>>> shares = SecretSharer.split_secret("c4bbcb1fbec99d65bf59d85c8cb62ee2db963f0fe106f483d9afa73bd4e39a8a", 2, 3)
['1-58cbd30524507e7a198bdfeb69c8d87fd7d2c10e8d5408851404f7d258cbcea7', '2-ecdbdaea89d75f8e73bde77a46db821cd40f430d39a11c864e5a4868dcb403ed', '3-80ebe2cfef5e40a2cdefef0923ee2bb9d04bc50be5ee308788af98ff609c380a']

...and recover secrets:

>>> SecretSharer.recover_secret(shares[0:3])
'c4bbcb1fbec99d65bf59d85c8cb62ee2db963f0fe106f483d9afa73bd4e39a8a'

And it supports a whole bunch of secret and share formats, like Bitcoin private keys and base32:

>>> from secretsharing import BitcoinToZB32SecretSharer
>>> shares = BitcoinToZB32SecretSharer.split_secret("5KJvsngHeMpm884wtkJNzQGaCErckhHJBGFsvd3VyK5qMZXj3hS", 2, 3)
['b-aweuzkm9jmfgd7x4k595bzcm3er3epf4dprfwzpprqa3exbuocs9byn4owfuqbo', 'n-btetgqqu8doacarsbyfdzpyycyj6gfdeaaxrpfx33pdjk4ou1d5owjdmdi1iegm9', 'd-njh33f14q7smucmh8iq8uaewc8mzub3mzptrwsegfiz3hc1fozkkjtguc4trh6sq']