To understand the problem, we first have to understand the file. The name breaks down into three parts:

In late 2019 and throughout 2020 and , the OpenSSL project officially ended support for the 1.0.x branch. This forced software maintainers and package managers (like the Cygwin setup program) to migrate to the newer 1.1.x branch.

If you are seeing a "missing" or "not found" error for cygcrypto11.dll , follow these steps to resolve it:

The file is a critical security library used by the Cygwin environment to provide OpenSSL cryptographic functions to Linux-based applications running on Windows. Core Functionality

environment, specifically providing the cryptographic functions of the OpenSSL 1.1 Stack Overflow