EVP_EncryptInit(3) OpenSSL EVP_EncryptInit(3) NNAAMMEE EVP_CIPHER_CTX_init, EVP_EncryptInit_ex, EVP_EncryptUpdate, EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptUpdate, EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherUpdate, EVP_CipherFi- nal_ex, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_cleanup, EVP_EncryptInit, EVP_EncryptFinal, EVP_Decryp- tInit, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal, EVP_get_cipherbyname, EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_nid, EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags, EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length, EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param, EVP_CIPHER_CTX_set_padding, EVP_enc_null, EVP_des_cbc, EVP_des_ecb, EVP_des_cfb, EVP_des_ofb, EVP_des_ede_cbc, EVP_des_ede, EVP_des_ede_ofb, EVP_des_ede_cfb, EVP_des_ede3_cbc, EVP_des_ede3, EVP_des_ede3_ofb, EVP_des_ede3_cfb, EVP_desx_cbc, EVP_rc4, EVP_rc4_40, EVP_rc4_hmac_md5, EVP_idea_cbc, EVP_idea_ecb, EVP_idea_cfb, EVP_idea_ofb, EVP_rc2_cbc, EVP_rc2_ecb, EVP_rc2_cfb, EVP_rc2_ofb, EVP_rc2_40_cbc, EVP_rc2_64_cbc, EVP_bf_cbc, EVP_bf_ecb, EVP_bf_cfb, EVP_bf_ofb, EVP_cast5_cbc, EVP_cast5_ecb, EVP_cast5_cfb, EVP_cast5_ofb, EVP_rc5_32_12_16_cbc, EVP_rc5_32_12_16_ecb, EVP_rc5_32_12_16_cfb, EVP_rc5_32_12_16_ofb, EVP_aes_128_gcm, EVP_aes_192_gcm, EVP_aes_256_gcm, EVP_aes_128_ccm, EVP_aes_192_ccm, EVP_aes_256_ccm, EVP_aes_128_cbc_hmac_sha1, EVP_aes_256_cbc_hmac_sha1, EVP_aes_128_cbc_hmac_sha256, EVP_aes_256_cbc_hmac_sha256 - EVP cipher routines SSYYNNOOPPSSIISS #include void EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a); int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, ENGINE *impl, const unsigned char *key, const unsigned char *iv); int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl, const unsigned char *in, int inl); int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl); int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, ENGINE *impl, const unsigned char *key, const unsigned char *iv); int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl, const unsigned char *in, int inl); int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl); int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc); int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl, const unsigned char *in, int inl); int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl); int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, const unsigned char *key, const unsigned char *iv); int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl); int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, const unsigned char *key, const unsigned char *iv); int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl); int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, const unsigned char *key, const unsigned char *iv, int enc); int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl); int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding); int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen); int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr); int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a); const EVP_CIPHER *EVP_get_cipherbyname(const char *name); #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a)) #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a)) #define EVP_CIPHER_nid(e) ((e)->nid) #define EVP_CIPHER_block_size(e) ((e)->block_size) #define EVP_CIPHER_key_length(e) ((e)->key_len) #define EVP_CIPHER_iv_length(e) ((e)->iv_len) #define EVP_CIPHER_flags(e) ((e)->flags) #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE) int EVP_CIPHER_type(const EVP_CIPHER *ctx); #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher) #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid) #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size) #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len) #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len) #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data) #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d)) #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c)) #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags) #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE) int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type); int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type); DDEESSCCRRIIPPTTIIOONN The EVP cipher routines are a high level interface to certain symmetric ciphers. _E_V_P___C_I_P_H_E_R___C_T_X___i_n_i_t_(_) initializes cipher contex ccttxx. _E_V_P___E_n_c_r_y_p_t_I_n_i_t___e_x_(_) sets up cipher context ccttxx for encryption with cipher ttyyppee from ENGINE iimmppll. ccttxx must be initialized before calling this function. ttyyppee is normally supplied by a function such as _E_V_P___a_e_s___2_5_6___c_b_c_(_). If iimmppll is NULL then the default implementation is used. kkeeyy is the symmetric key to use and iivv is the IV to use (if nec- essary), the actual number of bytes used for the key and IV depends on the cipher. It is possible to set all parameters to NULL except ttyyppee in an initial call and supply the remaining parameters in subsequent calls, all of which have ttyyppee set to NULL. This is done when the default cipher parameters are not appropriate. _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) encrypts iinnll bytes from the buffer iinn and writes the encrypted version to oouutt. This function can be called multiple times to encrypt successive blocks of data. The amount of data written depends on the block alignment of the encrypted data: as a result the amount of data written may be anything from zero bytes to (inl + cipher_block_size - 1) so oouutt should contain sufficient room. The actual number of bytes written is placed in oouuttll. If padding is enabled (the default) then _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l___e_x_(_) encrypts the "final" data, that is any data that remains in a partial block. It uses standard block padding (aka PKCS padding). The encrypted final data is written to oouutt which should have sufficient space for one cipher block. The number of bytes written is placed in oouuttll. After this function is called the encryption operation is finished and no further calls to _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) should be made. If padding is disabled then _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l___e_x_(_) will not encrypt any more data and it will return an error if any data remains in a partial block: that is if the total data length is not a multiple of the block size. _E_V_P___D_e_c_r_y_p_t_I_n_i_t___e_x_(_), _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) and _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l___e_x_(_) are the corresponding decryption operations. _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l_(_) will return an error code if padding is enabled and the final block is not cor- rectly formatted. The parameters and restrictions are identical to the encryption operations except that if padding is enabled the decrypted data buffer oouutt passed to _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) should have sufficient room for (iinnll + cipher_block_size) bytes unless the cipher block size is 1 in which case iinnll bytes is sufficient. _E_V_P___C_i_p_h_e_r_I_n_i_t___e_x_(_), _E_V_P___C_i_p_h_e_r_U_p_d_a_t_e_(_) and _E_V_P___C_i_p_h_e_r_F_i_n_a_l___e_x_(_) are functions that can be used for decryption or encryption. The operation performed depends on the value of the eenncc parameter. It should be set to 1 for encryption, 0 for decryption and -1 to leave the value unchanged (the actual value of 'enc' being supplied in a previous call). _E_V_P___C_I_P_H_E_R___C_T_X___c_l_e_a_n_u_p_(_) clears all information from a cipher context and free up any allocated memory associate with it. It should be called after all operations using a cipher are complete so sensitive informa- tion does not remain in memory. _E_V_P___E_n_c_r_y_p_t_I_n_i_t_(_), _E_V_P___D_e_c_r_y_p_t_I_n_i_t_(_) and _E_V_P___C_i_p_h_e_r_I_n_i_t_(_) behave in a similar way to _E_V_P___E_n_c_r_y_p_t_I_n_i_t___e_x_(_), EVP_DecryptInit_ex and _E_V_P___C_i_p_h_e_r_I_n_i_t___e_x_(_) except the ccttxx parameter does not need to be ini- tialized and they always use the default cipher implementation. _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l_(_), _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l_(_) and _E_V_P___C_i_p_h_e_r_F_i_n_a_l_(_) are iden- tical to _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l___e_x_(_), _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l___e_x_(_) and _E_V_P___C_i_p_h_e_r_F_i_- _n_a_l___e_x_(_). In previous releases they also cleaned up the ccttxx, but this is no longer done and _E_V_P___C_I_P_H_E_R___C_T_X___c_l_e_a_n_(_) must be called to free any context resources. _E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_a_m_e_(_), _E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_i_d_(_) and _E_V_P___g_e_t___c_i_p_h_e_r_b_y_o_b_j_(_) return an EVP_CIPHER structure when passed a cipher name, a NID or an ASN1_OBJECT structure. _E_V_P___C_I_P_H_E_R___n_i_d_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___n_i_d_(_) return the NID of a cipher when passed an EEVVPP__CCIIPPHHEERR or EEVVPP__CCIIPPHHEERR__CCTTXX structure. The actual NID value is an internal value which may not have a corresponding OBJECT IDENTIFIER. _E_V_P___C_I_P_H_E_R___C_T_X___s_e_t___p_a_d_d_i_n_g_(_) enables or disables padding. By default encryption operations are padded using standard block padding and the padding is checked and removed when decrypting. If the ppaadd parameter is zero then no padding is performed, the total amount of data encrypted or decrypted must then be a multiple of the block size or an error will occur. _E_V_P___C_I_P_H_E_R___k_e_y___l_e_n_g_t_h_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___k_e_y___l_e_n_g_t_h_(_) return the key length of a cipher when passed an EEVVPP__CCIIPPHHEERR or EEVVPP__CCIIPPHHEERR__CCTTXX struc- ture. The constant EEVVPP__MMAAXX__KKEEYY__LLEENNGGTTHH is the maximum key length for all ciphers. Note: although _E_V_P___C_I_P_H_E_R___k_e_y___l_e_n_g_t_h_(_) is fixed for a given cipher, the value of _E_V_P___C_I_P_H_E_R___C_T_X___k_e_y___l_e_n_g_t_h_(_) may be different for variable key length ciphers. _E_V_P___C_I_P_H_E_R___C_T_X___s_e_t___k_e_y___l_e_n_g_t_h_(_) sets the key length of the cipher ctx. If the cipher is a fixed length cipher then attempting to set the key length to any value other than the fixed value is an error. _E_V_P___C_I_P_H_E_R___i_v___l_e_n_g_t_h_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___i_v___l_e_n_g_t_h_(_) return the IV length of a cipher when passed an EEVVPP__CCIIPPHHEERR or EEVVPP__CCIIPPHHEERR__CCTTXX. It will return zero if the cipher does not use an IV. The constant EEVVPP__MMAAXX__IIVV__LLEENNGGTTHH is the maximum IV length for all ciphers. _E_V_P___C_I_P_H_E_R___b_l_o_c_k___s_i_z_e_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___b_l_o_c_k___s_i_z_e_(_) return the block size of a cipher when passed an EEVVPP__CCIIPPHHEERR or EEVVPP__CCIIPPHHEERR__CCTTXX structure. The constant EEVVPP__MMAAXX__IIVV__LLEENNGGTTHH is also the maximum block length for all ciphers. _E_V_P___C_I_P_H_E_R___t_y_p_e_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___t_y_p_e_(_) return the type of the passed cipher or context. This "type" is the actual NID of the cipher OBJECT IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and 128 bit RC2 have the same NID. If the cipher does not have an object identifier or does not have ASN1 support this function will return NNIIDD__uunnddeeff. _E_V_P___C_I_P_H_E_R___C_T_X___c_i_p_h_e_r_(_) returns the EEVVPP__CCIIPPHHEERR structure when passed an EEVVPP__CCIIPPHHEERR__CCTTXX structure. _E_V_P___C_I_P_H_E_R___m_o_d_e_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___m_o_d_e_(_) return the block cipher mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then EVP_CIPH_STREAM_CIPHER is returned. _E_V_P___C_I_P_H_E_R___p_a_r_a_m___t_o___a_s_n_1_(_) sets the AlgorithmIdentifier "parameter" based on the passed cipher. This will typically include any parameters and an IV. The cipher IV (if any) must be set when this call is made. This call should be made before the cipher is actually "used" (before any _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_), _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) calls for example). This function may fail if the cipher does not have any ASN1 support. _E_V_P___C_I_P_H_E_R___a_s_n_1___t_o___p_a_r_a_m_(_) sets the cipher parameters based on an ASN1 AlgorithmIdentifier "parameter". The precise effect depends on the cipher In the case of RC2, for example, it will set the IV and effec- tive key length. This function should be called after the base cipher type is set but before the key is set. For example _E_V_P___C_i_p_h_e_r_I_n_i_t_(_) will be called with the IV and key set to NULL, _E_V_P___C_I_P_H_E_R___a_s_n_1___t_o___p_a_r_a_m_(_) will be called and finally _E_V_P___C_i_p_h_e_r_I_n_i_t_(_) again with all parameters except the key set to NULL. It is possible for this function to fail if the cipher does not have any ASN1 support or the parameters cannot be set (for example the RC2 effective key length is not supported. _E_V_P___C_I_P_H_E_R___C_T_X___c_t_r_l_(_) allows various cipher specific parameters to be determined and set. RREETTUURRNN VVAALLUUEESS _E_V_P___E_n_c_r_y_p_t_I_n_i_t___e_x_(_), _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) and _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l___e_x_(_) return 1 for success and 0 for failure. _E_V_P___D_e_c_r_y_p_t_I_n_i_t___e_x_(_) and _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) return 1 for success and 0 for failure. _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l___e_x_(_) returns 0 if the decrypt failed or 1 for success. _E_V_P___C_i_p_h_e_r_I_n_i_t___e_x_(_) and _E_V_P___C_i_p_h_e_r_U_p_d_a_t_e_(_) return 1 for success and 0 for failure. _E_V_P___C_i_p_h_e_r_F_i_n_a_l___e_x_(_) returns 0 for a decryption failure or 1 for success. _E_V_P___C_I_P_H_E_R___C_T_X___c_l_e_a_n_u_p_(_) returns 1 for success and 0 for failure. _E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_a_m_e_(_), _E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_i_d_(_) and _E_V_P___g_e_t___c_i_p_h_e_r_b_y_o_b_j_(_) return an EEVVPP__CCIIPPHHEERR structure or NULL on error. _E_V_P___C_I_P_H_E_R___n_i_d_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___n_i_d_(_) return a NID. _E_V_P___C_I_P_H_E_R___b_l_o_c_k___s_i_z_e_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___b_l_o_c_k___s_i_z_e_(_) return the block size. _E_V_P___C_I_P_H_E_R___k_e_y___l_e_n_g_t_h_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___k_e_y___l_e_n_g_t_h_(_) return the key length. _E_V_P___C_I_P_H_E_R___C_T_X___s_e_t___p_a_d_d_i_n_g_(_) always returns 1. _E_V_P___C_I_P_H_E_R___i_v___l_e_n_g_t_h_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___i_v___l_e_n_g_t_h_(_) return the IV length or zero if the cipher does not use an IV. _E_V_P___C_I_P_H_E_R___t_y_p_e_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___t_y_p_e_(_) return the NID of the cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER. _E_V_P___C_I_P_H_E_R___C_T_X___c_i_p_h_e_r_(_) returns an EEVVPP__CCIIPPHHEERR structure. _E_V_P___C_I_P_H_E_R___p_a_r_a_m___t_o___a_s_n_1_(_) and _E_V_P___C_I_P_H_E_R___a_s_n_1___t_o___p_a_r_a_m_(_) return 1 for success or zero for failure. CCIIPPHHEERR LLIISSTTIINNGG All algorithms have a fixed key length unless otherwise stated. _E_V_P___e_n_c___n_u_l_l_(_) Null cipher: does nothing. EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void) DES in CBC, ECB, CFB and OFB modes respectively. EVP_des_ede_cbc(void), _E_V_P___d_e_s___e_d_e_(_), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void) Two key triple DES in CBC, ECB, CFB and OFB modes respectively. EVP_des_ede3_cbc(void), _E_V_P___d_e_s___e_d_e_3_(_), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void) Three key triple DES in CBC, ECB, CFB and OFB modes respectively. EVP_desx_cbc(void) DESX algorithm in CBC mode. EVP_rc4(void) RC4 stream cipher. This is a variable key length cipher with default key length 128 bits. EVP_rc4_40(void) RC4 stream cipher with 40 bit key length. This is obsolete and new code should use _E_V_P___r_c_4_(_) and the _E_V_P___C_I_P_H_E_R___C_T_X___s_e_t___k_e_y___l_e_n_g_t_h_(_) function. _E_V_P___i_d_e_a___c_b_c_(_) EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void) IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respec- tively. EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void) RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respec- tively. This is a variable key length cipher with an additional parameter called "effective key bits" or "effective key length". By default both are set to 128 bits. EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void) RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits. These are obsolete and new code should use _E_V_P___r_c_2___c_b_c_(_), _E_V_P___C_I_P_H_E_R___C_T_X___s_e_t___k_e_y___l_e_n_g_t_h_(_) and _E_V_P___C_I_P_H_E_R___C_T_X___c_t_r_l_(_) to set the key length and effective key length. EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void); Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length cipher. EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void) CAST encryption algorithm in CBC, ECB, CFB and OFB modes respec- tively. This is a variable key length cipher. EVP_rc5_32_12_16_cbc(void), EVP_rc5_32_12_16_ecb(void), EVP_rc5_32_12_16_cfb(void), EVP_rc5_32_12_16_ofb(void) RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respec- tively. This is a variable key length cipher with an additional "number of rounds" parameter. By default the key length is set to 128 bits and 12 rounds. EVP_aes_128_gcm(void), EVP_aes_192_gcm(void), EVP_aes_256_gcm(void) AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respec- tively. These ciphers require additional control operations to function correctly: see "GCM mode" section below for details. EVP_aes_128_ccm(void), EVP_aes_192_ccm(void), EVP_aes_256_ccm(void) AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively. These ciphers require additional control operations to function correctly: see CCM mode section below for details. GGCCMM MMooddee For GCM mode ciphers the behaviour of the EVP interface is subtly altered and several GCM specific ctrl operations are supported. To specify any additional authenticated data (AAD) a call to _E_V_P___C_i_p_h_e_r_U_p_d_a_t_e_(_), _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) or _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) should be made with the output parameter oouutt set to NNUULLLL. When decrypting the return value of _E_V_P___D_e_c_r_y_p_t_F_i_n_a_l_(_) or _E_V_P___C_i_p_h_e_r_F_i_- _n_a_l_(_) indicates if the operation was successful. If it does not indi- cate success the authentication operation has failed and any output data MMUUSSTT NNOOTT be used as it is corrupted. The following ctrls are supported in GCM mode: EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, ivlen, NULL); Sets the GCM IV length: this call can only be made before specifying an IV. If not called a default IV length is used (96 bits for AES). EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, taglen, tag); Writes ttaagglleenn bytes of the tag value to the buffer indicated by ttaagg. This call can only be made when encrypting data and aafftteerr all data has been processed (e.g. after an _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l_(_) call). EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, taglen, tag); Sets the expected tag to ttaagglleenn bytes from ttaagg. This call is only legal when decrypting data. CCCCMM MMooddee The behaviour of CCM mode ciphers is similar to CCM mode but with a few additional requirements and different ctrl values. Like GCM mode any additional authenticated data (AAD) is passed by calling _E_V_P___C_i_p_h_e_r_U_p_d_a_t_e_(_), _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) or _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) with the output parameter oouutt set to NNUULLLL. Additionally the total plaintext or ciphertext length MMUUSSTT be passed to _E_V_P___C_i_p_h_e_r_U_p_d_a_t_e_(_), _E_V_P___E_n_c_r_y_p_t_U_p_d_a_t_e_(_) or _E_V_P___D_e_c_r_y_p_t_U_p_d_a_t_e_(_) with the output and input parameters (iinn and oouutt) set to NNUULLLL and the length passed in the iinnll parameter. The following ctrls are supported in CCM mode: EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_TAG, taglen, tag); This call is made to set the expected CCCCMM tag value when decrypting or the length of the tag (with the ttaagg parameter set to NULL) when encrypting. The tag length is often referred to as MM. If not set a default value is used (12 for AES). EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL); Sets the CCM LL value. If not set a default is used (8 for AES). EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_IVLEN, ivlen, NULL); Sets the CCM nonce (IV) length: this call can only be made before spec- ifying an nonce value. The nonce length is given by 1155 -- LL so it is 7 by default for AES. NNOOTTEESS Where possible the EEVVPP interface to symmetric ciphers should be used in preference to the low level interfaces. This is because the code then becomes transparent to the cipher used and much more flexible. Addi- tionally, the EEVVPP interface will ensure the use of platform specific cryptographic acceleration such as AES-NI (the low level interfaces do not provide the guarantee). PKCS padding works by adding nn padding bytes of value nn to make the total length of the encrypted data a multiple of the block size. Pad- ding is always added so if the data is already a multiple of the block size nn will equal the block size. For example if the block size is 8 and 11 bytes are to be encrypted then 5 padding bytes of value 5 will be added. When decrypting the final block is checked to see if it has the correct form. Although the decryption operation can produce an error if padding is enabled, it is not a strong test that the input data or key is correct. A random block has better than 1 in 256 chance of being of the correct format and problems with the input data earlier on will not produce a final decrypt error. If padding is disabled then the decryption operation will always suc- ceed if the total amount of data decrypted is a multiple of the block size. The functions _E_V_P___E_n_c_r_y_p_t_I_n_i_t_(_), _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l_(_), _E_V_P___D_e_c_r_y_p_t_I_n_i_t_(_), _E_V_P___C_i_p_h_e_r_I_n_i_t_(_) and _E_V_P___C_i_p_h_e_r_F_i_n_a_l_(_) are obsolete but are retained for compatibility with existing code. New code should use _E_V_P___E_n_c_r_y_p_- _t_I_n_i_t___e_x_(_), _E_V_P___E_n_c_r_y_p_t_F_i_n_a_l___e_x_(_), _E_V_P___D_e_c_r_y_p_t_I_n_i_t___e_x_(_), _E_V_P___D_e_c_r_y_p_t_F_i_- _n_a_l___e_x_(_), _E_V_P___C_i_p_h_e_r_I_n_i_t___e_x_(_) and _E_V_P___C_i_p_h_e_r_F_i_n_a_l___e_x_(_) because they can reuse an existing context without allocating and freeing it up on each call. BBUUGGSS For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is a limitation of the current RC5 code rather than the EVP inter- face. EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with default key lengths. If custom ciphers exceed these values the results are unpredictable. This is because it has become standard practice to define a generic key as a fixed unsigned char array con- taining EVP_MAX_KEY_LENGTH bytes. The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode. EEXXAAMMPPLLEESS Encrypt a string using IDEA: int do_crypt(char *outfile) { unsigned char outbuf[1024]; int outlen, tmplen; /* Bogus key and IV: we'd normally set these from * another source. */ unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}; unsigned char iv[] = {1,2,3,4,5,6,7,8}; char intext[] = "Some Crypto Text"; EVP_CIPHER_CTX ctx; FILE *out; EVP_CIPHER_CTX_init(&ctx); EVP_EncryptInit_ex(&ctx, EVP_idea_cbc(), NULL, key, iv); if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext))) { /* Error */ return 0; } /* Buffer passed to EVP_EncryptFinal() must be after data just * encrypted to avoid overwriting it. */ if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen)) { /* Error */ return 0; } outlen += tmplen; EVP_CIPHER_CTX_cleanup(&ctx); /* Need binary mode for fopen because encrypted data is * binary data. Also cannot use strlen() on it because * it wont be null terminated and may contain embedded * nulls. */ out = fopen(outfile, "wb"); fwrite(outbuf, 1, outlen, out); fclose(out); return 1; } The ciphertext from the above example can be decrypted using the ooppeennssssll utility with the command line (shown on two lines for clarity): openssl idea -d