Libcrypto
From AMule Project FAQ
What is Crypto++/Cryptopp ?
Crypto++ Library is a free C++ class library of cryptographic schemes.
aMule needed Crypto++/Cryptopp for Secure User Identification (SUI) from versions 2.0.0-rc1 to 2.0.0-rc5 (included).
Debian users should read Howto make Crypto++ work on Debian.
NOTE: aMule is a separate project and is not realated to Crypto++/Cryptopp in any way (apart from using it as one of it's libraries).