/usr/include/xsec/enc/ is in libxml-security-c-dev 1.7.2-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/xsec/enc/NSS/
/usr/include/xsec/enc/NSS/NSSCryptoHash.hpp
/usr/include/xsec/enc/NSS/NSSCryptoHashHMAC.hpp
/usr/include/xsec/enc/NSS/NSSCryptoKeyDSA.hpp
/usr/include/xsec/enc/NSS/NSSCryptoKeyHMAC.hpp
/usr/include/xsec/enc/NSS/NSSCryptoKeyRSA.hpp
/usr/include/xsec/enc/NSS/NSSCryptoProvider.hpp
/usr/include/xsec/enc/NSS/NSSCryptoSymmetricKey.hpp
/usr/include/xsec/enc/NSS/NSSCryptoX509.hpp
/usr/include/xsec/enc/OpenSSL/
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoBase64.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoHash.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoHashHMAC.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoKeyDSA.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoKeyEC.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoKeyHMAC.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoKeyRSA.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoProvider.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoSymmetricKey.hpp
/usr/include/xsec/enc/OpenSSL/OpenSSLCryptoX509.hpp
/usr/include/xsec/enc/XSCrypt/
/usr/include/xsec/enc/XSCrypt/XSCryptCryptoBase64.hpp
/usr/include/xsec/enc/XSECCryptoBase64.hpp
/usr/include/xsec/enc/XSECCryptoException.hpp
/usr/include/xsec/enc/XSECCryptoHash.hpp
/usr/include/xsec/enc/XSECCryptoKey.hpp
/usr/include/xsec/enc/XSECCryptoKeyDSA.hpp
/usr/include/xsec/enc/XSECCryptoKeyEC.hpp
/usr/include/xsec/enc/XSECCryptoKeyHMAC.hpp
/usr/include/xsec/enc/XSECCryptoKeyRSA.hpp
/usr/include/xsec/enc/XSECCryptoProvider.hpp
/usr/include/xsec/enc/XSECCryptoSymmetricKey.hpp
/usr/include/xsec/enc/XSECCryptoUtils.hpp
/usr/include/xsec/enc/XSECCryptoX509.hpp
/usr/include/xsec/enc/XSECKeyInfoResolver.hpp
/usr/include/xsec/enc/XSECKeyInfoResolverDefault.hpp