Task $1.$

Bojan's public key for the RSA system is $($n$,$ e$),$ where n $=899$ and e $=23.$

$1.$ Find the decryption exponent d $($assuming you know the split of the number n $=29\backslash$times $31).$

$2.$ Could Bojan choose an even number for the encryption exponent e$,$ for example e $=4?$

$3.$ Bojan sends his public key to Anita by email. Oskar intercepts the letter, changes the encryption exponent e $=23$ to e$0=17$ and forwards the letter to Anita. Anita z encrypts the text b with the key $($n$,$ e$0)$ and sends it to Bojan. Of course, Bojan cannot decipher the message and sends Anita his public key again. Anita encrypts message b again, this time with the key $($n$,$ e$)$ and sends it to Bojan. Oskar intercepted both of Anita's letters. Describe exactly how he can calculate the text b $($assuming he does not know the factorization of the number n or the decoding of the exponent d$).$