Pros of OpenSSL

• Wider adoption and more extensive ecosystem support
• More frequent updates and feature additions
• Broader platform compatibility

Cons of OpenSSL

• Larger codebase, potentially more complex to maintain
• Historical security vulnerabilities due to legacy code
• Slower to remove deprecated or insecure features

Code Comparison

OpenSSL:

int SSL_CTX_use_certificate_file(SSL_CTX *ctx, const char *file, int type)
{
    int j;
    BIO *in;
    int ret = 0;
    X509 *x = NULL;

LibreSSL:

int
SSL_CTX_use_certificate_file(SSL_CTX *ctx, const char *file, int type)
{
	int ret;
	BIO *in;
	X509 *x = NULL;

LibreSSL's implementation is slightly more concise, reflecting its focus on simplicity and code cleanliness. OpenSSL's version includes an additional variable declaration and a more complex structure, which aligns with its broader feature set and compatibility requirements.

Both projects aim to provide secure cryptographic libraries, but LibreSSL focuses on streamlining and improving security, while OpenSSL maintains a wider range of features and compatibility. The choice between them often depends on specific project requirements and security priorities.

Pros of BoringSSL

• More actively maintained with frequent updates and contributions
• Designed for performance and optimized for modern systems
• Includes additional features and APIs tailored for Google's infrastructure

Cons of BoringSSL

• Less focus on broad compatibility across different platforms
• May have a steeper learning curve due to its specialized nature
• Not intended as a drop-in replacement for OpenSSL in all scenarios

Code Comparison

BoringSSL:

#include <openssl/ssl.h>

SSL_CTX *ctx = SSL_CTX_new(TLS_method());
SSL_CTX_set_min_proto_version(ctx, TLS1_2_VERSION);

LibreSSL:

#include <openssl/ssl.h>

SSL_CTX *ctx = SSL_CTX_new(TLSv1_2_method());
SSL_CTX_set_options(ctx, SSL_OP_NO_TLSv1 | SSL_OP_NO_TLSv1_1);

Both libraries provide similar functionality, but BoringSSL offers more modern APIs and defaults to newer TLS versions. LibreSSL maintains closer compatibility with OpenSSL's API structure.

BoringSSL is tailored for Google's needs and may include optimizations specific to their use cases, while LibreSSL aims for broader compatibility and adherence to OpenSSL's API. Choose based on your project's requirements and target platforms.

Pros of Mbed-TLS

• More portable and lightweight, suitable for embedded systems and IoT devices
• Easier to integrate into existing projects due to its modular design
• Extensive documentation and examples for various use cases

Cons of Mbed-TLS

• Less comprehensive feature set compared to LibreSSL
• May have slower performance for some cryptographic operations
• Smaller community and less frequent updates

Code Comparison

Mbed-TLS (initializing an SSL context):

mbedtls_ssl_context ssl;
mbedtls_ssl_config conf;

mbedtls_ssl_init(&ssl);
mbedtls_ssl_config_init(&conf);
mbedtls_ssl_config_defaults(&conf, MBEDTLS_SSL_IS_CLIENT, MBEDTLS_SSL_TRANSPORT_STREAM, MBEDTLS_SSL_PRESET_DEFAULT);

LibreSSL (initializing an SSL context):

SSL_CTX *ctx;
SSL *ssl;

ctx = SSL_CTX_new(TLS_client_method());
ssl = SSL_new(ctx);
SSL_set_connect_state(ssl);

Both libraries provide similar functionality for SSL/TLS operations, but Mbed-TLS focuses on simplicity and portability, while LibreSSL offers a more comprehensive feature set and compatibility with OpenSSL. The choice between them depends on the specific requirements of your project, such as target platform, performance needs, and desired feature set.

Pros of wolfSSL

• Smaller footprint and faster performance, especially on embedded systems
• More extensive hardware cryptography support
• Broader platform compatibility, including RTOS and embedded systems

Cons of wolfSSL

• Less widely adopted compared to LibreSSL
• May require more manual configuration for certain use cases
• Smaller community and ecosystem

Code Comparison

wolfSSL example:

#include <wolfssl/ssl.h>

WOLFSSL_CTX* ctx = wolfSSL_CTX_new(wolfTLSv1_2_client_method());
WOLFSSL* ssl = wolfSSL_new(ctx);
wolfSSL_connect(ssl);

LibreSSL example:

#include <openssl/ssl.h>

SSL_CTX* ctx = SSL_CTX_new(TLSv1_2_client_method());
SSL* ssl = SSL_new(ctx);
SSL_connect(ssl);

Both libraries provide similar APIs, with wolfSSL using its own naming conventions. The core functionality remains comparable, but wolfSSL offers additional options for embedded systems and hardware acceleration.

Pros of s2n-tls

• Designed specifically for cloud environments, optimized for AWS services
• Smaller codebase, potentially easier to audit and maintain
• Focuses on a subset of TLS features, reducing complexity

Cons of s2n-tls

• Less comprehensive feature set compared to LibreSSL
• May not be as widely adopted or tested in diverse environments
• Potentially less suitable for general-purpose TLS implementations

Code Comparison

s2n-tls:

int s2n_negotiate(struct s2n_connection *conn, s2n_blocked_status *blocked)
{
    while (conn->mode != S2N_MODE_APP_DATA) {
        int r = s2n_handshake(conn, blocked);
        if (r < 0) {
            return r;
        }
    }
    return 0;
}

LibreSSL:

int
SSL_do_handshake(SSL *s)
{
    int ret = 1;

    if (s->handshake_func == NULL) {
        SSLerror(s, SSL_R_CONNECTION_TYPE_NOT_SET);
        return -1;
    }

    s->method->ssl_renegotiate_check(s);

    if ((ret = s->handshake_func(s)) <= 0)
        return ret;

    return 1;
}

The code snippets show different approaches to handling TLS handshakes. s2n-tls uses a simpler loop structure, while LibreSSL employs a more complex function with additional checks and error handling.

Pros of libsodium

• Focused on modern, high-security cryptographic primitives
• Easier to use API with fewer opportunities for misuse
• Cross-platform support with better portability

Cons of libsodium

• Smaller feature set compared to LibreSSL
• Less compatibility with legacy systems and protocols
• Not a drop-in replacement for OpenSSL in many cases

Code Comparison

LibreSSL (TLS connection):

SSL_CTX *ctx = SSL_CTX_new(TLS_client_method());
SSL *ssl = SSL_new(ctx);
SSL_set_fd(ssl, socket);
SSL_connect(ssl);

libsodium (Public-key encryption):

unsigned char pk[crypto_box_PUBLICKEYBYTES];
unsigned char sk[crypto_box_SECRETKEYBYTES];
crypto_box_keypair(pk, sk);
crypto_box_easy(ciphertext, message, message_len, nonce, pk, sk);

Summary

LibreSSL is a more comprehensive cryptographic library, offering a wider range of features and better compatibility with existing systems. libsodium, on the other hand, provides a more modern and user-friendly approach to cryptography, focusing on high-security primitives and ease of use. The choice between the two depends on specific project requirements, such as legacy support needs or the desire for a simpler API.