Shamira Changeset - 7c94e9b021f6

Changeset - 7c94e9b021f6

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Laman - 4 years ago 2020-04-13 13:50:53

prefixing shares with labels

3 files changed with 23 insertions and 11 deletions:

src/cli.py

src/condensed.py

src/shamira.py

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src/cli.py

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@@ @@ -25,12 +25,15 @@ def build_split_parser(parser): @@
 	encoding = parser.add_mutually_exclusive_group()
 	encoding.add_argument("--hex", action="store_true", help="encode shares' bytes as a hexadecimal string")
 	encoding.add_argument("--b32", action="store_true", help="encode shares' bytes as a base32 string")
 	encoding.add_argument("--b64", action="store_true", help="encode shares' bytes as a base64 string")
 	parser.add_argument("--label", help="any label to prefix the shares with")
 	parser.add_argument("--omit_k_n", action="store_true", help="suppress the default shares prefix")
 	parser.add_argument("secret", nargs="?", help="a secret to be split. Can be provided on the command line,"
 		" redirected through stdin, or will be asked for interactively.")
 	parser.set_defaults(func=_generate)
 def build_join_parser(parser):
@@ @@ -53,13 +56,13 @@ def _generate(args): @@
 	elif sys.stdin.isatty():  # input from terminal
 		secret = input("Enter your secret:\n")
 	else:  # redirected from other source
 		secret = sys.stdin.read()
 	try:
 		shares = generate(secret, args.k, args.n, encoding)
+		shares = generate(secret, args.k, args.n, encoding, label=args.label, omit_k_n=args.omit_k_n)
 		for s in shares:
 			print(s)
 	except SException as e:
 		print(e, file=sys.stderr)

src/condensed.py

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@@ @@ -55,13 +55,13 @@ import binascii @@
 class SException(Exception): pass
 def reconstruct_raw(*shares):
 	"""Tries to recover the secret from its shares.
 	:param shares: ((i, (bytes) share), ...)
+	:param shares: (((int) i, (bytes) share), ...)
 	:return: (bytes) reconstructed secret. Too few shares returns garbage."""
 	secret_len = len(shares[0][1])
 	res = [None]*secret_len
 	for i in range(secret_len):
 		points = [(x, s[i]) for (x, s) in shares]
 		res[i] = (get_constant_coef(*points))
@@ @@ -80,13 +80,13 @@ def reconstruct(*shares): @@
 	except UnicodeDecodeError:
 		raise SException('Failed to decode bytes to utf-8. Either you supplied invalid shares, or you missed the "raw" flag. Offending value: "{0}"'.format(bs))
 def decode(share):
 	try:
-		(i, _, share_str) = share.partition(".")
+		(*_, i, share_str) = share.split(".")
 		i = int(i)
 		if not 1<=i<=255:
 			raise SException("Malformed share: Failed 1<=k<=255, k={0}".format(i))
 		share_bytes = base64.b32decode(share_str)
 		return (i, share_bytes)

src/shamira.py

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@@ @@ -35,34 +35,43 @@ def generate_raw(secret, k, n): @@
 	return [(i+1, bytes([s[i] for s in shares])) for i in range(n)]
 def reconstruct_raw(*shares):
 	"""Tries to recover the secret from its shares.
 	:param shares: ((i, (bytes) share), ...)
 	:return: (bytes) reconstructed secret. Too few shares returns garbage."""
 	:param shares: (((int) i, (bytes) share), ...)
 	:return: (bytes) reconstructed secret. Too few shares return garbage."""
 	secret_len = len(shares[0][1])
 	res = [None]*secret_len
 	for i in range(secret_len):
 		points = [(x, s[i]) for (x, s) in shares]
 		res[i] = (gf256.get_constant_coef(*points))
 	return bytes(res)
 def generate(secret, k, n, encoding="b32"):
+def generate(secret, k, n, encoding="b32", label="", omit_k_n=False):
 	"""Wraps generate_raw().
 	:param secret: (str or bytes)
 	:param k: number of shares necessary for secret recovery
 	:param n: number of shares generated
 	:param encoding: {hex, b32, b64} desired output encoding. Hexadecimal, Base32 or Base64.
 	:param label: (str) any label to prefix the shares with
 	:param omit_k_n: (boolean) suppress the default shares prefix
 	:return: [(str) share, ...]"""
 	if isinstance(secret,str):
 		secret = secret.encode("utf-8")
 	shares = generate_raw(secret, k, n)
 	return [encode(s, encoding) for s in shares]
 	prefix = ""
 	if label:
 		prefix = label + "."
 	if not omit_k_n:
 		prefix += "{0}.{1}.".format(k, n)
 	return [prefix + encode(s, encoding) for s in shares]
 def reconstruct(*shares, encoding="", raw=False):
 	"""Wraps reconstruct_raw.
 	:param shares: ((str) share, ...)
@@ @@ -86,13 +95,13 @@ def encode(share, encoding="b32"): @@
 	(i, bs) = share
 	return "{0}.{1}".format(i, f(bs).decode("utf-8"))
 def decode(share, encoding="b32"):
 	try:
-		(i, _, share_str) = share.partition(".")
+		(*_, i, share_str) = share.split(".")
 		i = int(i)
 		if not 1<=i<=255:
 			raise MalformedShare("Malformed share: Failed 1<=k<=255, k={0}".format(i))
 		if encoding=="hex": f = base64.b16decode
 		elif encoding=="b32": f = base64.b32decode
 		else: f = base64.b64decode
@@ @@ -101,15 +110,15 @@ def decode(share, encoding="b32"): @@
 	except (ValueError, binascii.Error):
 		raise MalformedShare('Malformed share: share="{0}", encoding="{1}"'.format(share, encoding))
 def detect_encoding(shares):
 	classes = [
 		(re.compile(r"\d+\.([0-9A-F]{2})+"), "hex"),
 		(re.compile(r"\d+\.([A-Z2-7]{8})*([A-Z2-7]{8}|[A-Z2-7]{2}={6}|[A-Z2-7]{4}={4}|[A-Z2-7]{5}={3}|[A-Z2-7]{7}={1})"), "b32"),
 		(re.compile(r"\d+\.([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{2}={2}|[A-Za-z0-9+/]{3}={1})"), "b64")
 		(re.compile(r"(.*\.)?\d+\.([0-9A-F]{2})+"), "hex"),
 		(re.compile(r"(.*\.)?\d+\.([A-Z2-7]{8})*([A-Z2-7]{8}|[A-Z2-7]{2}={6}|[A-Z2-7]{4}={4}|[A-Z2-7]{5}={3}|[A-Z2-7]{7}={1})"), "b32"),
 		(re.compile(r"(.*\.)?\d+\.([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{2}={2}|[A-Za-z0-9+/]{3}={1})"), "b64")
+	]
 	for (regexp, res) in classes:
 		if all(regexp.fullmatch(share) for share in shares):
 			return res
 	raise DetectionException("No expected encoding detected")

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