Subsystems

The cross-cutting machinery inside libcrypto that every other piece relies on. These pages cover internal building blocks rather than user-visible features.

Page	Source	One-liner
core-and-libctx	crypto/context.c, crypto/core_*.c, crypto/property/, crypto/provider*.c	The library context, the namemap, the property store, fetch and dispatch.
evp	crypto/evp/	The algorithm-agnostic API the rest of OpenSSL uses.
asn1	crypto/asn1/	ASN.1 templates, encode/decode, type system.
bio	crypto/bio/	The buffered/streaming I/O abstraction.
error-handling	crypto/err/	The error stack and *err.h machinery.
threading	crypto/threads_*.c, crypto/thread/	Locks, atomics, thread-local state, RCU.
memory	crypto/mem.c, crypto/mem_sec.c	General and secure heap allocation.
random	crypto/rand/, providers/implementations/rands/	DRBG hierarchy and entropy sources.

For user-visible features built on top of these subsystems (TLS, QUIC, X.509, CMS, …), see features.