Common use of Memory Requirements Clause in Contracts

Memory Requirements. During execution, RAM is required for some counters, the pairwise key, some temporary data, the Nη2 numbers in the pairwise key set and the counterpart’s public keys. While the mη elements of the public keys need to be computed, it is possible to write the code such that only one element is used at a time, requiring only one memory space in RAM. Overall, the largest amount of RAM required is for the pairwise key, QR = Nη2×b bits, where b is the data size in bits. Since our typical prime modulus is p ≤ 31, i.e., b ≤ 5 bits, we can simplify coding if we use one byte for the data size. The private key set requires the largest storage, Qo = ηNm×b bits, or Qo = ηNm bytes if one byte is used to store each b bit integer. As it is static, it can be stored in ROM. Input: Neighbour node’s public ID Output: The pairwise key Kpair Generate all the public key seeds for each public key seed do generate public key vector (mod q) for each private key do multiply with the public key vector (mod p) save result in key set R end end for each Ri do end Kpair = Kpair · (Ri + 1) (mod Sk) Listing 1: BYka pairwise key computation pseudo code.

Memory Requirements. During execution, RAM is required for some counters, the pairwise key, some temporary data, the Nη2 numbers in the pairwise key set and the counterpart’s public keys. While the mη elements of the public keys need to be computed, it is possible to write the code such that only one element is used at a time, requiring only one memory space in RAM. Overall, the largest amount of RAM required is for the pairwise key, QR = Nη2×b bits, where b is the data size in bits. Since our typical prime modulus is p ≤ ™ 31, i.e., b ≤ ™ 5 bits, we can simplify coding if we use one byte for the data size. The private key set requires the largest storage, Qo = ηNm×b bits, or Qo = ηNm bytes if one byte is used to store each b bit integer. As it is static, it can be stored in ROM. Input: Neighbour node’s public ID Output: The pairwise key Kpair Generate all the public key seeds for each public key seed do generate public key vector (mod q) for each private key do multiply with the public key vector (mod p) save result in key set R end end for each Ri do end Kpair = Kpair · (Ri + 1) (mod Sk) Listing 1: BYka pairwise key computation pseudo code.