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ae.h
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/* ---------------------------------------------------------------------------
*
* AEAD API 0.12 - 23-MAY-2012
*
* This file gives an interface appropriate for many authenticated
* encryption with associated data (AEAD) implementations. It does not try
* to accommodate all possible options or limitations that an implementation
* might have -- you should consult the documentation of your chosen
* implementation to find things like RFC 5116 constants, alignment
* requirements, whether the incremental interface is supported, etc.
*
* This file is in the public domain. It is provided "as is", without
* warranty of any kind. Use at your own risk.
*
* Comments are welcome: Ted Krovetz <ted@krovetz>.
*
* ------------------------------------------------------------------------ */
#ifndef _AE_H_
#define _AE_H_
#ifdef __cplusplus
extern "C" {
#endif
/* --------------------------------------------------------------------------
*
* Constants
*
* ----------------------------------------------------------------------- */
/* Return status codes: Negative return values indicate an error occurred.
* For full explanations of error values, consult the implementation's
* documentation. */
#define AE_SUCCESS (0) /* Indicates successful completion of call */
#define AE_INVALID (-1) /* Indicates bad tag during decryption */
#define AE_NOT_SUPPORTED (-2) /* Indicates unsupported option requested */
/* Flags: When data can be processed "incrementally", these flags are used
* to indicate whether the submitted data is the last or not. */
#define AE_FINALIZE (1) /* This is the last of data */
#define AE_PENDING (0) /* More data of is coming */
/* --------------------------------------------------------------------------
*
* AEAD opaque structure definition
*
* ----------------------------------------------------------------------- */
typedef struct _ae_ctx ae_ctx;
/* --------------------------------------------------------------------------
*
* Data Structure Routines
*
* ----------------------------------------------------------------------- */
ae_ctx* ae_allocate(void* misc); /* Allocate ae_ctx, set optional ptr */
void ae_free(ae_ctx* ctx); /* Deallocate ae_ctx struct */
int ae_clear(ae_ctx* ctx); /* Undo initialization */
int ae_ctx_sizeof(void); /* Return sizeof(ae_ctx) */
/* ae_allocate() allocates an ae_ctx structure, but does not initialize it.
* ae_free() deallocates an ae_ctx structure, but does not zero it.
* ae_clear() zeroes sensitive values associated with an ae_ctx structure
* and deallocates any auxiliary structures allocated during ae_init().
* ae_ctx_sizeof() returns sizeof(ae_ctx), to aid in any static allocations.
*/
/* --------------------------------------------------------------------------
*
* AEAD Routines
*
* ----------------------------------------------------------------------- */
int ae_init(ae_ctx* ctx, const void* key, int key_len, int nonce_len, int tag_len);
/* --------------------------------------------------------------------------
*
* Initialize an ae_ctx context structure.
*
* Parameters:
* ctx - Pointer to an ae_ctx structure to be initialized
* key - Pointer to user-supplied key
* key_len - Length of key supplied, in bytes
* nonce_len - Length of nonces to be used for this key, in bytes
* tag_len - Length of tags to be produced for this key, in bytes
*
* Returns:
* AE_SUCCESS - Success. Ctx ready for use.
* AE_NOT_SUPPORTED - An unsupported length was supplied. Ctx is untouched.
* Otherwise - Error. Check implementation documentation for codes.
*
* ----------------------------------------------------------------------- */
int ae_encrypt(ae_ctx* ctx, const void* nonce, const void* pt, int pt_len, const void* ad,
int ad_len, void* ct, void* tag, int final);
/* --------------------------------------------------------------------------
*
* Encrypt plaintext; provide for authentication of ciphertext/associated data.
*
* Parameters:
* ctx - Pointer to an ae_ctx structure initialized by ae_init.
* nonce - Pointer to a nonce_len (defined in ae_init) byte nonce.
* pt - Pointer to plaintext bytes to be encrypted.
* pt_len - number of bytes pointed to by pt.
* ad - Pointer to associated data.
* ad_len - number of bytes pointed to by ad.
* ct - Pointer to buffer to receive ciphertext encryption.
* tag - Pointer to receive authentication tag; or NULL
* if tag is to be bundled into the ciphertext.
* final - Non-zero if this call completes the plaintext being encrypted.
*
* If nonce!=NULL then a message is being initiated. If final!=0
* then a message is being finalized. If final==0 or nonce==NULL
* then the incremental interface is being used. If nonce!=NULL and
* ad_len<0, then use same ad as last message.
*
* Returns:
* non-negative - Number of bytes written to ct.
* AE_NOT_SUPPORTED - Usage mode unsupported (eg, incremental and/or sticky).
* Otherwise - Error. Check implementation documentation for codes.
*
* ----------------------------------------------------------------------- */
int ae_decrypt(ae_ctx* ctx, const void* nonce, const void* ct, int ct_len, const void* ad,
int ad_len, void* pt, const void* tag, int final);
/* --------------------------------------------------------------------------
*
* Decrypt ciphertext; provide authenticity of plaintext and associated data.
*
* Parameters:
* ctx - Pointer to an ae_ctx structure initialized by ae_init.
* nonce - Pointer to a nonce_len (defined in ae_init) byte nonce.
* ct - Pointer to ciphertext bytes to be decrypted.
* ct_len - number of bytes pointed to by ct.
* ad - Pointer to associated data.
* ad_len - number of bytes pointed to by ad.
* pt - Pointer to buffer to receive plaintext decryption.
* tag - Pointer to tag_len (defined in ae_init) bytes; or NULL
* if tag is bundled into the ciphertext. Non-NULL tag is only
* read when final is non-zero.
* final - Non-zero if this call completes the ciphertext being decrypted.
*
* If nonce!=NULL then "ct" points to the start of a ciphertext. If final!=0
* then "in" points to the final piece of ciphertext. If final==0 or nonce==
* NULL then the incremental interface is being used. If nonce!=NULL and
* ad_len<0, then use same ad as last message.
*
* Returns:
* non-negative - Number of bytes written to pt.
* AE_INVALID - Authentication failure.
* AE_NOT_SUPPORTED - Usage mode unsupported (eg, incremental and/or sticky).
* Otherwise - Error. Check implementation documentation for codes.
*
* NOTE !!! NOTE !!! -- The ciphertext should be assumed possibly inauthentic
* until it has been completely written and it is
* verified that this routine did not return AE_INVALID.
*
* ----------------------------------------------------------------------- */
#ifdef __cplusplus
} /* closing brace for extern "C" */
#endif
#endif /* _AE_H_ */