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cfb (cipher feedback) is the best mode for encrypting byte streams where single bytes must be encrypted.
since data there is short and random, the disadvantages of ecb have a favorable negative effect.

php does not support encrypting/decrypting bit streams currently. as of now, php only supports handling of strings.
some other mode and random device constants:

cbc (cipher block chaining) is especially suitable for encrypting files where the security is increased over ecb significantly.
for a more complete reference and discussion see applied cryptography by schneier (isbn 0-471-11709-9).

ecb (electronic codebook) is suitable for random data, such as encrypting other keys. since data there is short and random, the disadvantages of ecb have a favorable negative effect.
if linked against libmcrypt-2.4.x or higher the functions can also operate in the block cipher mode nofb and in stream mode.

this module uses the functions of openssl for generation and verification of signatures and for sealing (encrypting) and opening (decrypting) data. openssl offers many features that this module currently doesn't support. some of these may be added in the future.
openssl offers many features that this module currently doesn 't support.