Problems in ot_store

[maths644311798]

(1) In /crypto/primitives/ot/ot_store, SliceBase::ConsistencyCheck():

YACL_ENFORCE(internal_buf_size_ > internal_buf_ctr_, "Slice out of range!");

If the buf is fully used, then internal_buf_ctr_ should equal internal_buf_size_. Actually, the Reset() function makes internal_buf_ctr_= internal_buf_size_ hold. YACL_ENFORCE(internal_buf_size_ > internal_buf_ctr_ should be YACL_ENFORCE(internal_buf_size_ >= internal_buf_ctr_.
(2) In OtSendStore::GetBlock,

uint128_t OtSendStore::GetBlock(uint64_t ot_idx, uint64_t msg_idx) const {
  YACL_ENFORCE(msg_idx == 0 || msg_idx == 1);
  const uint64_t ot_blk_num = (type_ == OtStoreType::Compact) ? 1 : 2;
  if (delta_ == 0) {  // rot must be normal mode
    return blk_buf_->operator[](GetBufIdx(2 * ot_idx) + msg_idx);
  } else {  // cot could be normal mode or compact mode
    return blk_buf_->operator[](GetBufIdx(ot_blk_num * ot_idx)) ^
           (delta_ * msg_idx);
  }
}

In the normal mode for COT, for a specific slice, GetBlock[] never visits blk_buf_->[](2k+1), where k is an integer. Half of the buffer is wasted. Should COT only have compact mode?

[liang-xiaojian]

Thanks for your comments.

YACL_ENFORCE(internal_buf_size_ > internal_buf_ctr_ should be YACL_ENFORCE(internal_buf_size_ >= internal_buf_ctr_

Yes, internal_buf_ctr_ could be equal to internal_buf_size_. When it happens, the corresponding ot_store might not be able to generate a NextSlice, but it is still considered a valid state.

Should COT only have compact mode?

Good idea. In the initial design phase, we think we might support converting a CotSendStore to a RotSendStore. For this reason, normal mode COT could transform into ROT through ParaCrHashInplace without extra memory allocation.

By the way, we would redesign ot_store in recent times. :)

[maths644311798]

I would like to pull a request for fixing some typos and deleting #include "yacl/crypto/primitives/ot/gywz_ote.h" in gywz_ote.h.