Quoted from [Wikipedia][1]Wikipedia:
The Alice and Bob characters were invented by Ron Rivest, Adi Shamir, and Leonard Adleman in their 1978 paper "A method for obtaining digital signatures and public-key cryptosystems".
Rivest, R. L.; Shamir, A.; Adleman, L., A method for obtaining digital signatures and public-key cryptosystems, Commun. ACM 21, 120-126 (1978). ZBL0368.94005. [1]: https://en.wikipedia.org/wiki/Alice_and_Bob