This is the command ssss-combine that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
ssss - Split and Combine Secrets using Shamir's Secret Sharing Scheme.
SYNOPSIS
ssss-split -t threshold -n shares [-w token] [-s level] [-x] [-q] [-Q] [-D] [-v]
ssss-combine -t threshold [-x] [-q] [-Q] [-D] [-v]
DESCRIPTION
ssss is an implementation of Shamir's Secret Sharing Scheme. The program suite does both:
the generation of shares for a known secret, and the reconstruction of a secret using
user-provided shares.
COMMANDS
ssss-split: prompt the user for a secret and generate a set of corresponding shares.
ssss-combine: read in a set of shares and reconstruct the secret.
OPTIONS
-t threshold
Specify the number of shares necessary to reconstruct the secret.
-n shares
Specify the number of shares to be generated.
-w token
Text token to name shares in order to avoid confusion in case one utilizes secret
sharing to protect several independent secrets. The generated shares are prefixed
by these tokens.
-s level
Enforce the scheme's security level (in bits). This option implies an upper bound
for the length of the shared secret (shorter secrets are padded). Only multiples of
8 in the range from 8 to 1024 are allowed. If this option is omitted (or the value
given is 0) the security level is chosen automatically depending on the secret's
length. The security level directly determines the length of the shares.
-x Hex mode: use hexadecimal digits in place of ASCII characters for I/O. This is
useful if one wants to protect binary data, like block cipher keys.
-q Quiet mode: disable all unnecessary output. Useful in scripts.
-Q Extra quiet mode: like -q, but also suppress warnings.
-D Disable the diffusion layer added in version 0.2. This option is needed when shares
are combined that where generated with ssss version 0.1.
-v Print version information.
EXAMPLE
In case you want to protect your login password with a set of ten shares in such a way
that any three of them can reconstruct the password, you simply run the command
ssss-split -t 3 -n 10 -w passwd
To reconstruct the password pass three of the generated shares (in any order) to
ssss-combine -t 3
NOTES
To protect a secret larger than 1024 bits a hybrid technique has to be applied: encrypt
the secret with a block cipher and apply secret sharing to just the key. Among others
openssl and gpg can do the encryption part:
openssl bf -e < file.plain > file.encrypted
gpg -c < file.plain > file.encrypted
SECURITY
ssss tries to lock its virtual address space into RAM for privacy reasons. But this may
fail for two reasons: either the current uid doesn't permit page locking, or the
RLIMIT_MEMLOCK is set too low. After printing a warning message ssss will run even without
obtaining the desired mlock.
Use ssss-combine online using onworks.net services
