Question

how can we discribe symmetric

Answer 1

 Of a relation R on a setS, such that xRy if and only if yRx for all members x and y of S (that is, if the relation holds between any element and a second, it also holds between the second and the first)."Is a sibling of" is a symmetric relation.(cryptography) Using the same key (or keys that are trivially related) for both encryption and decryption.