Disabling TLS 1.0 and 1.1 in DC++ by 2020

Following the IETF’s deprecation of TLS 1.0 and TLS 1.1, Chrome, Edge, Firefox, and Safari have announced that they’ll disable both TLS 1.0 and 1.1 during the first half of 2020. GitHub, Stripe, CloudFlare, PayPal, and KeyCDN have all already done so on the server side. The deprecated TLS 1.0 dates from 1999 and TLS 1.1 from 2006.

Meanwhile, TLS 1.2 has now existed since 2008 and been supported by OpenSSL 1.0.1 since 2012. DC++, along therefore with modified versions, has supported TLS 1.2 since version 0.850 in 2015. ncdc likewise has supported TLS 1.2 for many years. ADCH++, uhub, and Luadch all support TLS 1.2 or 1.3.

Hardening DC++ Cryptography: TLS, HTTPS, and KEYP and BEAST, CRIME, BREACH, and Lucky 13: Assessing TLS in ADCS document vulnerabilities that TLS 1.0 and 1.1 allow or exacerbate, including but not limited to BEAST, Lucky 13, and potential downgrade attacks discovered in the future in TLS 1.0 or TLS 1.1 to which TLS 1.2 is not subject.

As such, DC++ has deprecated TLS 1.0 and 1.1 and will disable both by default in 2020 along with the browsers, while supporting TLS 1.2, 1.3, and newer versions, with an option to re-enable TLS 1.0 and 1.1 should that remain necessary.