#include "gnunet_common.h"
#include "gnunet_scheduler_lib.h"
+#include <gcrypt.h>
/**
*/
#define GNUNET_CRYPTO_HASH_LENGTH (512/8)
+/**
+ * How many characters (without 0-terminator) are our ASCII-encoded
+ * public keys (ECDSA/EDDSA/ECDHE).
+ */
+#define GNUNET_CRYPTO_PKEY_ASCII_LENGTH 52
+
/**
* @brief 0-terminated ASCII encoding of a struct GNUNET_HashCode.
*/
/**
- * @brief an ECC signature
+ * @brief an ECC signature using EdDSA.
+ * See https://gnunet.org/ed25519
+ */
+struct GNUNET_CRYPTO_EddsaSignature
+{
+
+ /**
+ * R value.
+ */
+ unsigned char r[256 / 8];
+
+ /**
+ * S value.
+ */
+ unsigned char s[256 / 8];
+
+};
+
+
+
+/**
+ * @brief an ECC signature using ECDSA
*/
-struct GNUNET_CRYPTO_EccSignature
+struct GNUNET_CRYPTO_EcdsaSignature
{
/**
/**
- * Public ECC key (always for NIST P-521) encoded in a format suitable
- * for network transmission and signatures (ECDSA/EdDSA).
+ * Public ECC key (always for Curve25519) encoded in a format suitable
+ * for network transmission and EdDSA signatures.
*/
-struct GNUNET_CRYPTO_EccPublicSignKey
+struct GNUNET_CRYPTO_EddsaPublicKey
{
/**
- * Q consists of an x- and a y-value, each mod p (256 bits),
- * given here in affine coordinates.
- *
- * FIXME: this coordinate will be removed in the future (compressed point!).
+ * Q consists of an x- and a y-value, each mod p (256 bits), given
+ * here in affine coordinates and Ed25519 standard compact format.
*/
- unsigned char q_x[256 / 8];
+ unsigned char q_y[256 / 8];
+};
+
+
+/**
+ * Public ECC key (always for Curve25519) encoded in a format suitable
+ * for network transmission and ECDSA signatures.
+ */
+struct GNUNET_CRYPTO_EcdsaPublicKey
+{
/**
- * Q consists of an x- and a y-value, each mod p (256 bits),
- * given here in affine coordinates.
+ * Q consists of an x- and a y-value, each mod p (256 bits), given
+ * here in affine coordinates and Ed25519 standard compact format.
*/
unsigned char q_y[256 / 8];
*/
struct GNUNET_PeerIdentity
{
- struct GNUNET_CRYPTO_EccPublicSignKey public_key;
+ struct GNUNET_CRYPTO_EddsaPublicKey public_key;
};
/**
- * Public ECC key (always for NIST P-521) encoded in a format suitable
- * for network transmission and encryption (ECDH).
+ * Public ECC key (always for Curve25519) encoded in a format suitable
+ * for network transmission and encryption (ECDH),
+ * See http://cr.yp.to/ecdh.html
*/
-struct GNUNET_CRYPTO_EccPublicEncryptKey
+struct GNUNET_CRYPTO_EcdhePublicKey
{
/**
- * Q consists of an x- and a y-value, each mod p (256 bits),
- * given here in affine coordinates.
+ * Q consists of an x- and a y-value, each mod p (256 bits), given
+ * here in affine coordinates and Ed25519 standard compact format.
*/
- unsigned char q_x[256 / 8];
+ unsigned char q_y[256 / 8];
+};
+
+/**
+ * Private ECC key encoded for transmission. To be used only for ECDH
+ * key exchange (ECDHE to be precise).
+ */
+struct GNUNET_CRYPTO_EcdhePrivateKey
+{
/**
- * Q consists of an x- and a y-value, each mod p (256 bits),
- * given here in affine coordinates.
- *
- * FIXME: this coordinate will be removed in the future (compressed point!).
+ * d is a value mod n, where n has at most 256 bits.
*/
- unsigned char q_y[256 / 8];
+ unsigned char d[256 / 8];
};
+/**
+ * Private ECC key encoded for transmission. To be used only for ECDSA
+ * signatures.
+ */
+struct GNUNET_CRYPTO_EcdsaPrivateKey
+{
+ /**
+ * d is a value mod n, where n has at most 256 bits.
+ */
+ unsigned char d[256 / 8];
+
+};
/**
- * Private ECC key encoded for transmission.
+ * Private ECC key encoded for transmission. To be used only for EdDSA
+ * signatures.
*/
-struct GNUNET_CRYPTO_EccPrivateKey
+struct GNUNET_CRYPTO_EddsaPrivateKey
{
/**
* d is a value mod n, where n has at most 256 bits.
};
+/**
+ * Size of paillier plain texts and public keys.
+ * Private keys and ciphertexts are twice this size.
+ */
+#define GNUNET_CRYPTO_PAILLIER_BITS 2048
+
+
+/**
+ * Paillier public key.
+ */
+struct GNUNET_CRYPTO_PaillierPublicKey
+{
+ /**
+ * N value.
+ */
+ unsigned char n[GNUNET_CRYPTO_PAILLIER_BITS / 8];
+};
+
+
+/**
+ * Paillier public key.
+ */
+struct GNUNET_CRYPTO_PaillierPrivateKey
+{
+ /**
+ * Lambda-component of the private key.
+ */
+ unsigned char lambda[GNUNET_CRYPTO_PAILLIER_BITS / 8];
+ /**
+ * Mu-component of the private key.
+ */
+ unsigned char mu[GNUNET_CRYPTO_PAILLIER_BITS / 8];
+};
+
+
+/**
+ * Paillier ciphertext.
+ */
+struct GNUNET_CRYPTO_PaillierCiphertext
+{
+ /**
+ * guaranteed minimum number of homomorphic operations with this ciphertext
+ */
+ int32_t remaining_ops GNUNET_PACKED;
+
+ /**
+ * The bits of the ciphertext.
+ */
+ unsigned char bits[GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8];
+};
+
+
/* **************** Functions and Macros ************* */
/**
GNUNET_CRYPTO_crc32_n (const void *buf, size_t len);
+/**
+ * @ingroup crypto
+ * Fill block with a random values.
+ *
+ * @param mode desired quality of the random number
+ * @param buffer the buffer to fill
+ * @param length buffer length
+ */
+void
+GNUNET_CRYPTO_random_block (enum GNUNET_CRYPTO_Quality mode, void *buffer, size_t length);
+
/**
* @ingroup crypto
* Produce a random value.
* Encrypt a block using a symmetric sessionkey.
*
* @param block the block to encrypt
- * @param len the size of the block
+ * @param size the size of the @a block
* @param sessionkey the key used to encrypt
* @param iv the initialization vector to use, use INITVALUE
* for streams.
* @return the size of the encrypted block, -1 for errors
*/
ssize_t
-GNUNET_CRYPTO_symmetric_encrypt (const void *block, size_t len,
+GNUNET_CRYPTO_symmetric_encrypt (const void *block, size_t size,
const struct GNUNET_CRYPTO_SymmetricSessionKey *sessionkey,
const struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
void *result);
* @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
* @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
* @param xts salt
- * @param xts_len length of xts
+ * @param xts_len length of @a xts
* @param skm source key material
- * @param skm_len length of skm
+ * @param skm_len length of @a skm
* @param ... pair of void * & size_t for context chunks, terminated by NULL
- * @return GNUNET_YES on success
+ * @return #GNUNET_YES on success
*/
int
GNUNET_CRYPTO_hkdf (void *result, size_t out_len, int xtr_algo, int prf_algo,
* @param xtr_algo hash algorithm for the extraction phase, GCRY_MD_...
* @param prf_algo hash algorithm for the expansion phase, GCRY_MD_...
* @param xts salt
- * @param xts_len length of xts
+ * @param xts_len length of @a xts
* @param skm source key material
- * @param skm_len length of skm
+ * @param skm_len length of @a skm
* @param argp va_list of void * & size_t pairs for context chunks
- * @return GNUNET_YES on success
+ * @return #GNUNET_YES on success
*/
int
GNUNET_CRYPTO_hkdf_v (void *result, size_t out_len, int xtr_algo, int prf_algo,
* @param result buffer for the derived key, allocated by caller
* @param out_len desired length of the derived key
* @param xts salt
- * @param xts_len length of xts
+ * @param xts_len length of @a xts
* @param skm source key material
- * @param skm_len length of skm
+ * @param skm_len length of @a skm
* @param argp va_list of void * & size_t pairs for context chunks
- * @return GNUNET_YES on success
+ * @return #GNUNET_YES on success
*/
int
GNUNET_CRYPTO_kdf_v (void *result, size_t out_len, const void *xts,
* @param result buffer for the derived key, allocated by caller
* @param out_len desired length of the derived key
* @param xts salt
- * @param xts_len length of xts
+ * @param xts_len length of @a xts
* @param skm source key material
- * @param skm_len length of skm
+ * @param skm_len length of @a skm
* @param ... void * & size_t pairs for context chunks
* @return #GNUNET_YES on success
*/
/**
- * Function called upon completion of 'GNUNET_CRYPTO_ecc_key_create_async'.
+ * @ingroup crypto
+ * Extract the public key for the given private key.
*
- * @param cls closure
- * @param pk NULL on error, otherwise the private key (which must be free'd by the callee)
- * @param emsg NULL on success, otherwise an error message
+ * @param priv the private key
+ * @param pub where to write the public key
*/
-typedef void (*GNUNET_CRYPTO_EccKeyCallback)(void *cls,
- struct GNUNET_CRYPTO_EccPrivateKey *pk,
- const char *emsg);
-
+void
+GNUNET_CRYPTO_ecdsa_key_get_public (const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
+ struct GNUNET_CRYPTO_EcdsaPublicKey *pub);
/**
* @ingroup crypto
* @param pub where to write the public key
*/
void
-GNUNET_CRYPTO_ecc_key_get_public_for_signature (const struct GNUNET_CRYPTO_EccPrivateKey *priv,
- struct GNUNET_CRYPTO_EccPublicSignKey *pub);
-
+GNUNET_CRYPTO_eddsa_key_get_public (const struct GNUNET_CRYPTO_EddsaPrivateKey *priv,
+ struct GNUNET_CRYPTO_EddsaPublicKey *pub);
/**
* @param pub where to write the public key
*/
void
-GNUNET_CRYPTO_ecc_key_get_public_for_encryption (const struct GNUNET_CRYPTO_EccPrivateKey *priv,
- struct GNUNET_CRYPTO_EccPublicEncryptKey *pub);
+GNUNET_CRYPTO_ecdhe_key_get_public (const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
+ struct GNUNET_CRYPTO_EcdhePublicKey *pub);
/**
* @return string representing @a pub
*/
char *
-GNUNET_CRYPTO_ecc_public_sign_key_to_string (const struct GNUNET_CRYPTO_EccPublicSignKey *pub);
+GNUNET_CRYPTO_ecdsa_public_key_to_string (const struct GNUNET_CRYPTO_EcdsaPublicKey *pub);
+
+
+/**
+ * Convert a public key to a string.
+ *
+ * @param pub key to convert
+ * @return string representing @a pub
+ */
+char *
+GNUNET_CRYPTO_eddsa_public_key_to_string (const struct GNUNET_CRYPTO_EddsaPublicKey *pub);
/**
* @return #GNUNET_OK on success
*/
int
-GNUNET_CRYPTO_ecc_public_sign_key_from_string (const char *enc,
- size_t enclen,
- struct GNUNET_CRYPTO_EccPublicSignKey *pub);
-
-
-
-/**
- * Convert a public key to a string.
- *
- * @param pub key to convert
- * @return string representing @a pub
- */
-char *
-GNUNET_CRYPTO_ecc_public_encrypt_key_to_string (const struct GNUNET_CRYPTO_EccPublicEncryptKey *pub);
+GNUNET_CRYPTO_ecdsa_public_key_from_string (const char *enc,
+ size_t enclen,
+ struct GNUNET_CRYPTO_EcdsaPublicKey *pub);
/**
* @return #GNUNET_OK on success
*/
int
-GNUNET_CRYPTO_ecc_public_encrypt_key_from_string (const char *enc,
- size_t enclen,
- struct GNUNET_CRYPTO_EccPublicEncryptKey *pub);
+GNUNET_CRYPTO_eddsa_public_key_from_string (const char *enc,
+ size_t enclen,
+ struct GNUNET_CRYPTO_EddsaPublicKey *pub);
/**
* @return new private key, NULL on error (for example,
* permission denied); free using #GNUNET_free
*/
-struct GNUNET_CRYPTO_EccPrivateKey *
-GNUNET_CRYPTO_ecc_key_create_from_file (const char *filename);
+struct GNUNET_CRYPTO_EcdsaPrivateKey *
+GNUNET_CRYPTO_ecdsa_key_create_from_file (const char *filename);
+
+
+/**
+ * @ingroup crypto
+ * Create a new private key by reading it from a file. If the
+ * files does not exist, create a new key and write it to the
+ * file. Caller must free return value. Note that this function
+ * can not guarantee that another process might not be trying
+ * the same operation on the same file at the same time.
+ * If the contents of the file
+ * are invalid the old file is deleted and a fresh key is
+ * created.
+ *
+ * @param filename name of file to use to store the key
+ * @return new private key, NULL on error (for example,
+ * permission denied); free using #GNUNET_free
+ */
+struct GNUNET_CRYPTO_EddsaPrivateKey *
+GNUNET_CRYPTO_eddsa_key_create_from_file (const char *filename);
/**
* @return new private key, NULL on error (for example,
* permission denied); free using #GNUNET_free
*/
-struct GNUNET_CRYPTO_EccPrivateKey *
-GNUNET_CRYPTO_ecc_key_create_from_configuration (const struct GNUNET_CONFIGURATION_Handle *cfg);
+struct GNUNET_CRYPTO_EddsaPrivateKey *
+GNUNET_CRYPTO_eddsa_key_create_from_configuration (const struct GNUNET_CONFIGURATION_Handle *cfg);
+
+
+/**
+ * @ingroup crypto
+ * Create a new private key. Caller must free return value.
+ *
+ * @return fresh private key; free using #GNUNET_free
+ */
+struct GNUNET_CRYPTO_EcdsaPrivateKey *
+GNUNET_CRYPTO_ecdsa_key_create (void);
+
+
+/**
+ * @ingroup crypto
+ * Create a new private key. Caller must free return value.
+ *
+ * @return fresh private key; free using #GNUNET_free
+ */
+struct GNUNET_CRYPTO_EddsaPrivateKey *
+GNUNET_CRYPTO_eddsa_key_create (void);
/**
*
* @return fresh private key; free using #GNUNET_free
*/
-struct GNUNET_CRYPTO_EccPrivateKey *
-GNUNET_CRYPTO_ecc_key_create (void);
+struct GNUNET_CRYPTO_EcdhePrivateKey *
+GNUNET_CRYPTO_ecdhe_key_create (void);
/**
* @param pk location of the key
*/
void
-GNUNET_CRYPTO_ecc_key_clear (struct GNUNET_CRYPTO_EccPrivateKey *pk);
+GNUNET_CRYPTO_eddsa_key_clear (struct GNUNET_CRYPTO_EddsaPrivateKey *pk);
+
+
+/**
+ * @ingroup crypto
+ * Clear memory that was used to store a private key.
+ *
+ * @param pk location of the key
+ */
+void
+GNUNET_CRYPTO_ecdsa_key_clear (struct GNUNET_CRYPTO_EcdsaPrivateKey *pk);
+
+/**
+ * @ingroup crypto
+ * Clear memory that was used to store a private key.
+ *
+ * @param pk location of the key
+ */
+void
+GNUNET_CRYPTO_ecdhe_key_clear (struct GNUNET_CRYPTO_EcdhePrivateKey *pk);
/**
*
* @return "anonymous" private key; do not free
*/
-const struct GNUNET_CRYPTO_EccPrivateKey *
-GNUNET_CRYPTO_ecc_key_get_anonymous (void);
+const struct GNUNET_CRYPTO_EcdsaPrivateKey *
+GNUNET_CRYPTO_ecdsa_key_get_anonymous (void);
/**
* @param cfg_name name of the configuration file to use
*/
void
-GNUNET_CRYPTO_ecc_setup_hostkey (const char *cfg_name);
+GNUNET_CRYPTO_eddsa_setup_hostkey (const char *cfg_name);
/**
GNUNET_CRYPTO_get_peer_identity (const struct GNUNET_CONFIGURATION_Handle *cfg,
struct GNUNET_PeerIdentity *dst);
+/**
+ * Compare two Peer Identities.
+ *
+ * @param first first peer identity
+ * @param second second peer identity
+ * @return bigger than 0 if first > second,
+ * 0 if they are the same
+ * smaller than 0 if second > first
+ */
+int
+GNUNET_CRYPTO_cmp_peer_identity (const struct GNUNET_PeerIdentity *first,
+ const struct GNUNET_PeerIdentity *second);
+
/**
* @ingroup crypto
* Derive key material from a public and a private ECC key.
*
* @param priv private key to use for the ECDH (x)
- * @param pub public key to use for the ECDY (yG)
+ * @param pub public key to use for the ECDH (yG)
* @param key_material where to write the key material (xyG)
* @return #GNUNET_SYSERR on error, #GNUNET_OK on success
*/
int
-GNUNET_CRYPTO_ecc_ecdh (const struct GNUNET_CRYPTO_EccPrivateKey *priv,
- const struct GNUNET_CRYPTO_EccPublicEncryptKey *pub,
+GNUNET_CRYPTO_ecc_ecdh (const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
+ const struct GNUNET_CRYPTO_EcdhePublicKey *pub,
struct GNUNET_HashCode *key_material);
/**
* @ingroup crypto
- * Sign a given block.
+ * EdDSA sign a given block.
*
* @param priv private key to use for the signing
* @param purpose what to sign (size, purpose)
* @return #GNUNET_SYSERR on error, #GNUNET_OK on success
*/
int
-GNUNET_CRYPTO_ecc_sign (const struct GNUNET_CRYPTO_EccPrivateKey *priv,
- const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
- struct GNUNET_CRYPTO_EccSignature *sig);
+GNUNET_CRYPTO_eddsa_sign (const struct GNUNET_CRYPTO_EddsaPrivateKey *priv,
+ const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+ struct GNUNET_CRYPTO_EddsaSignature *sig);
/**
* @ingroup crypto
- * Verify signature.
+ * ECDSA Sign a given block.
+ *
+ * @param priv private key to use for the signing
+ * @param purpose what to sign (size, purpose)
+ * @param sig where to write the signature
+ * @return #GNUNET_SYSERR on error, #GNUNET_OK on success
+ */
+int
+GNUNET_CRYPTO_ecdsa_sign (const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
+ const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
+ struct GNUNET_CRYPTO_EcdsaSignature *sig);
+
+/**
+ * @ingroup crypto
+ * Verify EdDSA signature.
*
* @param purpose what is the purpose that the signature should have?
* @param validate block to validate (size, purpose, data)
* @returns #GNUNET_OK if ok, #GNUNET_SYSERR if invalid
*/
int
-GNUNET_CRYPTO_ecc_verify (uint32_t purpose,
- const struct GNUNET_CRYPTO_EccSignaturePurpose *validate,
- const struct GNUNET_CRYPTO_EccSignature *sig,
- const struct GNUNET_CRYPTO_EccPublicSignKey *pub);
+GNUNET_CRYPTO_eddsa_verify (uint32_t purpose,
+ const struct GNUNET_CRYPTO_EccSignaturePurpose *validate,
+ const struct GNUNET_CRYPTO_EddsaSignature *sig,
+ const struct GNUNET_CRYPTO_EddsaPublicKey *pub);
+
+
+
+/**
+ * @ingroup crypto
+ * Verify ECDSA signature.
+ *
+ * @param purpose what is the purpose that the signature should have?
+ * @param validate block to validate (size, purpose, data)
+ * @param sig signature that is being validated
+ * @param pub public key of the signer
+ * @returns #GNUNET_OK if ok, #GNUNET_SYSERR if invalid
+ */
+int
+GNUNET_CRYPTO_ecdsa_verify (uint32_t purpose,
+ const struct GNUNET_CRYPTO_EccSignaturePurpose *validate,
+ const struct GNUNET_CRYPTO_EcdsaSignature *sig,
+ const struct GNUNET_CRYPTO_EcdsaPublicKey *pub);
/**
* typically the name of the subsystem/application
* @return derived private key
*/
-struct GNUNET_CRYPTO_EccPrivateKey *
-GNUNET_CRYPTO_ecc_key_derive (const struct GNUNET_CRYPTO_EccPrivateKey *priv,
- const char *label,
- const char *context);
+struct GNUNET_CRYPTO_EcdsaPrivateKey *
+GNUNET_CRYPTO_ecdsa_private_key_derive (const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
+ const char *label,
+ const char *context);
/**
* @param result where to write the derived public key
*/
void
-GNUNET_CRYPTO_ecc_public_key_derive (const struct GNUNET_CRYPTO_EccPublicSignKey *pub,
- const char *label,
- const char *context,
- struct GNUNET_CRYPTO_EccPublicSignKey *result);
+GNUNET_CRYPTO_ecdsa_public_key_derive (const struct GNUNET_CRYPTO_EcdsaPublicKey *pub,
+ const char *label,
+ const char *context,
+ struct GNUNET_CRYPTO_EcdsaPublicKey *result);
+
+
+/**
+ * Output the given MPI value to the given buffer in network
+ * byte order. The MPI @a val may not be negative.
+ *
+ * @param buf where to output to
+ * @param size number of bytes in @a buf
+ * @param val value to write to @a buf
+ */
+void
+GNUNET_CRYPTO_mpi_print_unsigned (void *buf,
+ size_t size,
+ gcry_mpi_t val);
+
+
+/**
+ * Convert data buffer into MPI value.
+ * The buffer is interpreted as network
+ * byte order, unsigned integer.
+ *
+ * @param result where to store MPI value (allocated)
+ * @param data raw data (GCRYMPI_FMT_USG)
+ * @param size number of bytes in @a data
+ */
+void
+GNUNET_CRYPTO_mpi_scan_unsigned (gcry_mpi_t *result,
+ const void *data,
+ size_t size);
+
+
+/**
+ * Create a freshly generated paillier public key.
+ *
+ * @param[out] public_key Where to store the public key?
+ * @param[out] private_key Where to store the private key?
+ */
+void
+GNUNET_CRYPTO_paillier_create (struct GNUNET_CRYPTO_PaillierPublicKey *public_key,
+ struct GNUNET_CRYPTO_PaillierPrivateKey *private_key);
+
+/**
+ * Encrypt a plaintext with a paillier public key.
+ *
+ * @param public_key Public key to use.
+ * @param m Plaintext to encrypt.
+ * @param[out] ciphertext Encrytion of @a plaintext with @a public_key.
+ * @return guaranteed number of supported homomorphic operations
+ */
+int
+GNUNET_CRYPTO_paillier_encrypt (const struct GNUNET_CRYPTO_PaillierPublicKey *public_key,
+ const gcry_mpi_t m,
+ struct GNUNET_CRYPTO_PaillierCiphertext *ciphertext);
+
+
+/**
+ * Decrypt a paillier ciphertext with a private key.
+ *
+ * @param private_key Private key to use for decryption.
+ * @param public_key Public key to use for decryption.
+ * @param ciphertext Ciphertext to decrypt.
+ * @param[out] m Decryption of @a ciphertext with @private_key.
+ */
+void
+GNUNET_CRYPTO_paillier_decrypt (const struct GNUNET_CRYPTO_PaillierPrivateKey *private_key,
+ const struct GNUNET_CRYPTO_PaillierPublicKey *public_key,
+ const struct GNUNET_CRYPTO_PaillierCiphertext *ciphertext,
+ gcry_mpi_t m);
+
+
+/**
+ * Compute a ciphertext that represents the sum of the plaintext in @a x1 and @a x2
+ *
+ * Note that this operation can only be done a finite number of times
+ * before an overflow occurs.
+ *
+ * @param public_key Public key to use for encryption.
+ * @param c1 Paillier cipher text.
+ * @param c2 Paillier cipher text.
+ * @param[out] result Result of the homomorphic operation.
+ * @return #GNUNET_OK if the result could be computed,
+ * #GNUNET_SYSERR if no more homomorphic operations are remaining.
+ */
+int
+GNUNET_CRYPTO_paillier_hom_add (const struct GNUNET_CRYPTO_PaillierPublicKey *public_key,
+ const struct GNUNET_CRYPTO_PaillierCiphertext *c1,
+ const struct GNUNET_CRYPTO_PaillierCiphertext *c2,
+ struct GNUNET_CRYPTO_PaillierCiphertext *result);
+
+
+/**
+ * Get the number of remaining supported homomorphic operations.
+ *
+ * @param c Paillier cipher text.
+ * @return the number of remaining homomorphic operations
+ */
+int
+GNUNET_CRYPTO_paillier_hom_get_remaining (const struct GNUNET_CRYPTO_PaillierCiphertext *c);
#if 0 /* keep Emacsens' auto-indent happy */
{