Sporadic failures when sending private transactions

[sebaraba]

The v-offset is set to 37 or 38 for private transactions. This helps quorum understand whether we are dealing with a private or non-private transaction. At the moment the v-offset is manipulated as follows:

 private fun setPrivate(message: ByteArray): ByteArray {
       val vOffset = message.size - 67
       when (message[vOffset]) {
           28.toByte() -> message[vOffset] = 38
           else -> message[vOffset] = 37
       }
       return message
   }

To identify the v-offset we made a naive assumption that signature data will always have the same length. Thus we would find the v-offset just before the 67th byte starting at the end of the payload. However, after more testings, we learned that the length of the signed that might vary.
A proposed solution to overcome this problem would adapting the setPrivate() method to something similar to this:

   private fun setPrivate(message: ByteArray): ByteArray {
       val rlpList = RlpDecoder.decode(message).values[0]
       if ( rlpList is RlpList) {
           val rlpListSize = rlpList.values.size
           val vField = rlpList.values[rlpListSize - 3]
           if (vField is RlpString) {
               when (vField.bytes[0]) {
                   28.toByte() -> vField.bytes[0] = 38
                   else -> vField.bytes[0] = 37
               }
           }
           return RlpEncoder.encode(rlpList)
       }
       return message
   }

Using an RLP decoder we can make sure that what we never miss the position of the v-offset in the signed data.

[stale]

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