  In this article, a classification of all the $(\sigma, \tau)$-derivations of
group algebras is given in terms of the generators and relators of a group. If
$R$ is a commutative ring and $G = \langle X \mid Y\rangle$ is a group with $X$
as its set of generators and $Y$ as a set of relators, then a necessary and
sufficient condition is developed for a map $f:X \rightarrow RG$ to be uniquely
extendable to a $(\sigma, \tau)$-derivation $D$ of $RG$, where $(\sigma, \tau)$
is a pair of endomorphisms of $RG$ which are $R$-linear extensions of the group
homomorphisms of $G$. It is also illustrated via a counterexample that the
condition of commutativity of $R$ is necessary and hence cannot be dropped.
Amongst several results established as applications of the above proved
results, a classification of all the $\sigma$-derivations of commutative group
algebras over a field of positive characteristic is given.
