--- /dev/null
+/* ppp-crypto.h - Generic API for access to crypto/digest functions.
+ *
+ * Copyright (c) 2022 Eivind Næss. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * 3. The name(s) of the authors of this software must not be used to
+ * endorse or promote products derived from this software without
+ * prior written permission.
+ *
+ * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
+ * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+ * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+ * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef PPP_CRYPTO_H
+#define PPP_CRYPTO_H
+
+#ifndef MD5_DIGEST_LENGTH
+#define MD5_DIGEST_LENGTH 16
+#endif
+
+#ifndef MD4_DIGEST_LENGTH
+#define MD4_DIGEST_LENGTH 16
+#endif
+
+#ifndef SHA_DIGEST_LENGTH
+#define SHA_DIGEST_LENGTH 20
+#endif
+
+struct _PPP_MD_CTX;
+struct _PPP_MD;
+
+typedef struct _PPP_MD_CTX PPP_MD_CTX;
+typedef struct _PPP_MD PPP_MD;
+
+/*
+ * Create a new Message Digest context object
+ */
+PPP_MD_CTX *PPP_MD_CTX_new();
+
+/*
+ * Free the Message Digest context
+ */
+void PPP_MD_CTX_free(PPP_MD_CTX*);
+
+/*
+ * Fetch the MD4 algorithm
+ */
+const PPP_MD *PPP_md4(void);
+
+/*
+ * Fetch the MD5 algorithm
+ */
+const PPP_MD *PPP_md5(void);
+
+/*
+ * Fetch the SHA1 algorithm
+ */
+const PPP_MD *PPP_sha1(void);
+
+/*
+ * Initializes a context object
+ */
+int PPP_DigestInit(PPP_MD_CTX *ctx,
+ const PPP_MD *type);
+
+/*
+ * For each iteration update the context with more input
+ */
+int PPP_DigestUpdate(PPP_MD_CTX *ctx,
+ const void *data, size_t cnt);
+
+/*
+ * Perform the final operation, and output the digest
+ */
+int PPP_DigestFinal(PPP_MD_CTX *ctx,
+ unsigned char *out, unsigned int *outlen);
+
+
+struct _PPP_CIPHER_CTX;
+struct _PPP_CIPHER;
+
+typedef struct _PPP_CIPHER_CTX PPP_CIPHER_CTX;
+typedef struct _PPP_CIPHER PPP_CIPHER;
+
+
+/*
+ * Create a new Cipher Context
+ */
+PPP_CIPHER_CTX *PPP_CIPHER_CTX_new(void);
+
+/*
+ * Release the Cipher Context
+ */
+void PPP_CIPHER_CTX_free(PPP_CIPHER_CTX *ctx);
+
+/*
+ * Fetch the DES in ECB mode cipher algorithm
+ */
+const PPP_CIPHER *PPP_des_ecb(void);
+
+/*
+ * Set the particular data directly
+ */
+void PPP_CIPHER_CTX_set_cipher_data(PPP_CIPHER_CTX *ctx,
+ const unsigned char *key);
+
+/*
+ * Initialize the crypto operation
+ */
+int PPP_CipherInit(PPP_CIPHER_CTX *ctx,
+ const PPP_CIPHER *cipher,
+ const unsigned char *key,
+ const unsigned char *iv,
+ int encr);
+
+/*
+ * Encrypt input data, and store it in the output buffer
+ */
+int PPP_CipherUpdate(PPP_CIPHER_CTX *ctx,
+ unsigned char *out, int *outl,
+ const unsigned char *in, int inl);
+
+/*
+ * Finish the crypto operation, and fetch any outstanding bytes
+ */
+int PPP_CipherFinal(PPP_CIPHER_CTX *ctx,
+ unsigned char *out, int *outl);
+
+/*
+ * Global initialization, must be called once per process
+ */
+int PPP_crypto_init();
+
+/*
+ * Global deinitialization
+ */
+int PPP_crypto_deinit();
+
+#endif