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Dummy pro signature should be generated from throwaway keys #79

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Merged
jagerman merged 1 commit into from
Feb 18, 2026
Merged

Dummy pro signature should be generated from throwaway keys #79

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37 changes: 24 additions & 13 deletions src/session_protocol.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -506,19 +506,30 @@ static EncryptedForDestinationInternal encode_for_destination_internal(
envelope.set_content(content.data(), content.size());

// Generate the session pro signature. If there's no pro ed25519 key specified, we still
// fill out the pro signature with a dummy 64 byte stream. This is to make pro and
// non-pro messages indistinguishable.
std::string* pro_sig = envelope.mutable_prosig();
pro_sig->resize(crypto_sign_ed25519_BYTES);
if (dest_pro_rotating_ed25519_privkey.empty()) {
randombytes_buf(pro_sig->data(), pro_sig->size());
} else {
crypto_sign_ed25519_detached(
reinterpret_cast<uint8_t*>(pro_sig->data()),
nullptr,
content.data(),
content.size(),
dest_pro_rotating_ed25519_privkey.data());
// fill out the pro signature with a valid but unverifiable signature by creating a
// throw-away key. This makes pro and non-pro messages indistinguishable on the wire.
{
std::string* pro_sig = envelope.mutable_prosig();
pro_sig->resize(crypto_sign_ed25519_BYTES);

if (dest_pro_rotating_ed25519_privkey.empty()) {
uc32 ignore_pk;
cleared_uc64 dummy_pro_ed_sk;
crypto_sign_ed25519_keypair(ignore_pk.data(), dummy_pro_ed_sk.data());
crypto_sign_ed25519_detached(
reinterpret_cast<uint8_t*>(pro_sig->data()),
nullptr,
content.data(),
content.size(),
dummy_pro_ed_sk.data());
} else {
crypto_sign_ed25519_detached(
reinterpret_cast<uint8_t*>(pro_sig->data()),
nullptr,
content.data(),
content.size(),
dest_pro_rotating_ed25519_privkey.data());
}
}

if (is_group) {
Expand Down