\\ Assume given the RSA triple (publick,secret,modulus) this
\\ implements encryption and decryption of messages.

\\ One should probably use the bit-picking
\\ operators in pari to give left-right exponentiation

expon(base,exponent,modulus)=
{
	local(u,p);
	u=1;p=block;
	while(exponent>0,
		if( exponent%2 != 0,
			u = (u*p)%modulus;
		);
		exponent=exponent\2;
		p=(p*p)%modulus;
	)
	return(u);
}

\\ small message blocks should probably be 
\\ given some random additional noise!

encrypt(key,modulus,message)=
{
	local(channel);
	channel=0;
	block=message%(modulus-1);
	while(block != 0,
		channel=channel*(modulus-1)+expon(block,key,modulus);
		message=message \ (modulus-1);
		block=message%(modulus-1);
	);
}

decrypt(key,modulus,channel)=
{
	encrypt(key,modulus,channel); // Entirely symmetric key !!!
}