I have implemented a ECC key generation scheme successfully. Now I need to find ECC key sizes of each generating key pairs. I assumed that ECC key size is the size of the ECC private Key. So I would like to to know whether it is correct?
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ECC public keys are (X,Y) points where X and Y are elements in a given field (e.g. Fp or F2m).
For example, secp160r1 uses a 160-bit prime field. X and Y can be up to 160 bits long. So (X,Y) is 320 bits.
The (X,Y) point can be represented in compressed form where only the X value and a bit of information is given, since Y is a function of X.
X.962 encoding can be used for these 3 cases. Note that X and Y are zero-padded to the prime modulus size in the case they are smaller:
0x04 | X | Y
Compressed (Y is even):
0x02 | X
Compressed (Y is odd):
0x03 | X