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BBS+: add some checks on disclosed indexes array #949

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merged 3 commits into from
Oct 24, 2024
Merged

BBS+: add some checks on disclosed indexes array #949

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c07a48d
fix: add some checks on disclosed indexes array
FilippoTrotter Oct 14, 2024
027df2a
fix(bbs): better error handling for disclosed indexes array
FilippoTrotter Oct 15, 2024
3e9a952
add explanatory comment on BBS+ indexes error handling
FilippoTrotter Oct 21, 2024
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31 changes: 25 additions & 6 deletions src/lua/crypto_bbs.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -644,16 +644,19 @@ local function core_proof_gen(ciphersuite, pk, signature, generators, header, ph
local signature_result = octets_to_signature(signature)
local AA, e = table.unpack(signature_result)
local undisclosed_indexes = {}
local disclosed_messages = {}
local undisclosed_messages = {}
for i, v in ipairs(disclosed_indexes) do
if i > 1 and disclosed_indexes[i] == disclosed_indexes[i - 1] then --Arrays are always sorted in proof_gen (line 684) before being passed as input to core_proof_gen
error('disclosed indexes contains duplicates', 3)
end
table.insert(disclosed_messages, messages[v])
end
for i = 1, L do
if not array_contains(disclosed_indexes, i) then
table.insert(undisclosed_indexes, i)
end
end
local disclosed_messages = {}
local undisclosed_messages = {}
for _,v in ipairs(disclosed_indexes) do
table.insert(disclosed_messages, messages[v])
end
for _,v in ipairs(undisclosed_indexes) do
table.insert(undisclosed_messages, messages[v])
end
Expand All @@ -679,6 +682,12 @@ function bbs.proof_gen(ciphersuite, pk, signature, header, ph, messages, disclos
header = header or O.empty()
ph = ph or O.empty()
table.sort(disclosed_indexes) -- make sure indexes are sorted
if disclosed_indexes[1] <= 0 then
error('Disclosed indexes contains an integer less than or equal to 0', 2)
end
if disclosed_indexes[#disclosed_indexes] > #messages then
error('Disclosed index contains an integer which exceeds the total number of messages', 2)
end
local messages = bbs.messages_to_scalars(ciphersuite,messages)
local generators = bbs.create_generators(ciphersuite, table_size(messages) + 1)
local proof = core_proof_gen(ciphersuite, pk, signature, generators, header, ph, messages, disclosed_indexes)
Expand Down Expand Up @@ -830,7 +839,17 @@ function bbs.proof_verify(ciphersuite, pk, proof, header, ph, disclosed_messages
disclosed_indexes = disclosed_indexes or {}
local len_U = math.floor((#proof-proof_len_floor)/OCTET_SCALAR_LENGTH)
local len_R = table_size(disclosed_indexes)

if disclosed_indexes[1] <= 0 then
error('Disclosed indexes contains an integer less than or equal to 0', 2)
end
if disclosed_indexes[#disclosed_indexes] > len_R+len_U then
error('Disclosed index contains an integer which exceeds the total number of messages', 2)
end
for i = 2, len_R, 1 do
if disclosed_indexes[i] == disclosed_indexes[i - 1] then
error('disclosed indexes contains duplicates', 2)
end
end
local message_scalars = bbs.messages_to_scalars(ciphersuite, disclosed_messages_octets)
local generators = bbs.create_generators(ciphersuite, len_U+len_R+1)

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