X-Git-Url: http://git.osdn.net/view?a=blobdiff_plain;f=third-party%2Fopenssl-1.0.2d%2Fdoc%2Fcrypto%2FEVP_EncryptInit.pod;fp=third-party%2Fopenssl-1.0.2d%2Fdoc%2Fcrypto%2FEVP_EncryptInit.pod;h=fb6036f959ba0ce01ad27c2045a9f01368a5a810;hb=3d0f5661d0cd3583f7d7b0b8158703b6cb3a4e4d;hp=0000000000000000000000000000000000000000;hpb=071cc1ce9be277e9175381194150b7b5461bd586;p=wordring-tm%2Fwordring-tm.git diff --git a/third-party/openssl-1.0.2d/doc/crypto/EVP_EncryptInit.pod b/third-party/openssl-1.0.2d/doc/crypto/EVP_EncryptInit.pod new file mode 100644 index 0000000..fb6036f --- /dev/null +++ b/third-party/openssl-1.0.2d/doc/crypto/EVP_EncryptInit.pod @@ -0,0 +1,593 @@ +=pod + +=head1 NAME + +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_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length, +EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_cleanup, EVP_EncryptInit, +EVP_EncryptFinal, EVP_DecryptInit, 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_idea_cbc, +EVP_idea_ecb, EVP_idea_cfb, EVP_idea_ofb, EVP_idea_cbc, 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 cipher routines + +=head1 SYNOPSIS + + #include + + void EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a); + + int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type, + ENGINE *impl, unsigned char *key, unsigned char *iv); + int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, + int *outl, 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, unsigned char *key, unsigned char *iv); + int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, + int *outl, 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, unsigned char *key, unsigned char *iv, int enc); + int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, + int *outl, 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, + unsigned char *key, 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, + unsigned char *key, 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, + unsigned char *key, 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); + +=head1 DESCRIPTION + +The EVP cipher routines are a high level interface to certain +symmetric ciphers. + +EVP_CIPHER_CTX_init() initializes cipher contex B. + +EVP_EncryptInit_ex() sets up cipher context B for encryption +with cipher B from ENGINE B. B must be initialized +before calling this function. B is normally supplied +by a function such as EVP_des_cbc(). If B is NULL then the +default implementation is used. B is the symmetric key to use +and B is the IV to use (if necessary), 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 B in an initial call and supply +the remaining parameters in subsequent calls, all of which have B +set to NULL. This is done when the default cipher parameters are not +appropriate. + +EVP_EncryptUpdate() encrypts B bytes from the buffer B and +writes the encrypted version to B. 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 B should contain sufficient +room. The actual number of bytes written is placed in B. + +If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts +the "final" data, that is any data that remains in a partial block. +It uses L (aka PKCS padding). The encrypted +final data is written to B which should have sufficient space for +one cipher block. The number of bytes written is placed in B. After +this function is called the encryption operation is finished and no further +calls to EVP_EncryptUpdate() should be made. + +If padding is disabled then EVP_EncryptFinal_ex() 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. + +EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the +corresponding decryption operations. EVP_DecryptFinal() will return an +error code if padding is enabled and the final block is not correctly +formatted. The parameters and restrictions are identical to the encryption +operations except that if padding is enabled the decrypted data buffer B +passed to EVP_DecryptUpdate() should have sufficient room for +(B + cipher_block_size) bytes unless the cipher block size is 1 in +which case B bytes is sufficient. + +EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are +functions that can be used for decryption or encryption. The operation +performed depends on the value of the B 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). + +EVP_CIPHER_CTX_cleanup() 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 information +does not remain in memory. + +EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a +similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex and +EVP_CipherInit_ex() except the B parameter does not need to be +initialized and they always use the default cipher implementation. + +EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() behave in a +similar way to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and +EVP_CipherFinal_ex() except B is automatically cleaned up +after the call. + +EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj() +return an EVP_CIPHER structure when passed a cipher name, a NID or an +ASN1_OBJECT structure. + +EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when +passed an B or B structure. The actual NID +value is an internal value which may not have a corresponding OBJECT +IDENTIFIER. + +EVP_CIPHER_CTX_set_padding() 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 B 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. + +EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key +length of a cipher when passed an B or B +structure. The constant B is the maximum key length +for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a +given cipher, the value of EVP_CIPHER_CTX_key_length() may be different +for variable key length ciphers. + +EVP_CIPHER_CTX_set_key_length() 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. + +EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV +length of a cipher when passed an B or B. +It will return zero if the cipher does not use an IV. The constant +B is the maximum IV length for all ciphers. + +EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block +size of a cipher when passed an B or B +structure. The constant B is also the maximum block +length for all ciphers. + +EVP_CIPHER_type() and EVP_CIPHER_CTX_type() 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 +B. + +EVP_CIPHER_CTX_cipher() returns the B structure when passed +an B structure. + +EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() 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. + +EVP_CIPHER_param_to_asn1() 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 +EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function +may fail if the cipher does not have any ASN1 support. + +EVP_CIPHER_asn1_to_param() 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 effective key length. +This function should be called after the base cipher type is set but before +the key is set. For example EVP_CipherInit() will be called with the IV and +key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally +EVP_CipherInit() 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. + +EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined +and set. + +=head1 RETURN VALUES + +EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex() +return 1 for success and 0 for failure. + +EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure. +EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success. + +EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure. +EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success. + +EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure. + +EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj() +return an B structure or NULL on error. + +EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID. + +EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block +size. + +EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key +length. + +EVP_CIPHER_CTX_set_padding() always returns 1. + +EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV +length or zero if the cipher does not use an IV. + +EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's +OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER. + +EVP_CIPHER_CTX_cipher() returns an B structure. + +EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for +success or zero for failure. + +=head1 CIPHER LISTING + +All algorithms have a fixed key length unless otherwise stated. + +=over 4 + +=item EVP_enc_null() + +Null cipher: does nothing. + +=item 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. + +=item EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void) + +Two key triple DES in CBC, ECB, CFB and OFB modes respectively. + +=item EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void) + +Three key triple DES in CBC, ECB, CFB and OFB modes respectively. + +=item EVP_desx_cbc(void) + +DESX algorithm in CBC mode. + +=item EVP_rc4(void) + +RC4 stream cipher. This is a variable key length cipher with default key length 128 bits. + +=item EVP_rc4_40(void) + +RC4 stream cipher with 40 bit key length. This is obsolete and new code should use EVP_rc4() +and the EVP_CIPHER_CTX_set_key_length() function. + +=item EVP_idea_cbc() 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 respectively. + +=item 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 respectively. 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. + +=item 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 EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and +EVP_CIPHER_CTX_ctrl() to set the key length and effective key length. + +=item 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. + +=item 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 respectively. This is a variable key +length cipher. + +=item 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 respectively. 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. + +=item 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 respectively. +These ciphers require additional control operations to function correctly: see +L section below for details. + +=item 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. + +=back + +=head1 GCM Mode + +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 EVP_CipherUpdate(), +EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output +parameter B set to B. + +When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal() +indicates if the operation was successful. If it does not indicate success +the authentication operation has failed and any output data B +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 B bytes of the tag value to the buffer indicated by B. +This call can only be made when encrypting data and B all data has been +processed (e.g. after an EVP_EncryptFinal() call). + + EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, taglen, tag); + +Sets the expected tag to B bytes from B. This call is only legal +when decrypting data and must be made B any data is processed (e.g. +before any EVP_DecryptUpdate() call). + +See L below for an example of the use of GCM mode. + +=head1 CCM Mode + +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 +EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output +parameter B set to B. Additionally the total plaintext or ciphertext +length B be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or +EVP_DecryptUpdate() with the output and input parameters (B and B) +set to B and the length passed in the B 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 B tag value when decrypting or +the length of the tag (with the B parameter set to NULL) when encrypting. +The tag length is often referred to as B. 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 B 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 specifying +an nonce value. The nonce length is given by B<15 - L> so it is 7 by default +for AES. + + + +=head1 NOTES + +Where possible the B 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. Additionally, the +B 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 B padding bytes of value B to make the total +length of the encrypted data a multiple of the block size. Padding is always +added so if the data is already a multiple of the block size B 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 succeed if +the total amount of data decrypted is a multiple of the block size. + +The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(), +EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for +compatibility with existing code. New code should use EVP_EncryptInit_ex(), +EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(), +EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an +existing context without allocating and freeing it up on each call. + +=head1 BUGS + +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 interface. + +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 containing 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. + +=head1 EXAMPLES + +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 B +utility with the command line (shown on two lines for clarity): + + openssl idea -d + +=head1 HISTORY + +EVP_CIPHER_CTX_init(), EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(), +EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(), EVP_CipherInit_ex(), +EVP_CipherFinal_ex() and EVP_CIPHER_CTX_set_padding() appeared in +OpenSSL 0.9.7. + +IDEA appeared in OpenSSL 0.9.7 but was often disabled due to +patent concerns; the last patents expired in 2012. + +=cut