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Digg  mcrypt_enc_get_key_size
Returns the maximum supported keysize of the opened mode
(PHP 4 >= 4.0.2, PHP 5)
Code Examples / Notes » mcrypt_enc_get_key_sizeterry _at_ scribendi_com
The key size returned by this function is for keys consisting of 8-bit characters. For example, 256-bit algorithms require 32-character keys. However, if you are using alphanumeric keys [A-Za-z0-9] beware that strength is reduced, because you are only using a set of 64 characters, which could be represented in 6 bits. You get: 6 x 32 = 192-bit encryption. Avoid using string representations hashes - md5() or sha1() - because hex encoding uses a set of only 16 characters [0-9a-f], which is equivalent to 4 bits, and thus halve the strength of your encryption: 4 x 32 = 128-bit. A 64 character hex representation of an SHA-256 hash will not improve matters, because only the first 32 characters can be used. You need an 8-bit representation of SHA-256, or of two MD5s, to get full 256-bit strength. The problem is somewhat reduced in OFB, CFB or CBC mode by the use of IVs, but only if you do not package your IV with the encrypted data. |
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mcrypt_cbc mcrypt_cfb mcrypt_create_iv mcrypt_decrypt mcrypt_ecb mcrypt_enc_get_algorithms_name mcrypt_enc_get_block_size mcrypt_enc_get_iv_size mcrypt_enc_get_key_size mcrypt_enc_get_modes_name mcrypt_enc_get_supported_key_sizes mcrypt_enc_is_block_algorithm_mode mcrypt_enc_is_block_algorithm mcrypt_enc_is_block_mode mcrypt_enc_self_test mcrypt_encrypt mcrypt_generic_deinit mcrypt_generic_end mcrypt_generic_init mcrypt_generic mcrypt_get_block_size mcrypt_get_cipher_name mcrypt_get_iv_size mcrypt_get_key_size mcrypt_list_algorithms mcrypt_list_modes mcrypt_module_close mcrypt_module_get_algo_block_size mcrypt_module_get_algo_key_size mcrypt_module_get_supported_key_sizes mcrypt_module_is_block_algorithm_mode mcrypt_module_is_block_algorithm mcrypt_module_is_block_mode mcrypt_module_open mcrypt_module_self_test mcrypt_ofb mdecrypt_generic |
