SHA-3

Giriş
Standart SHA-3 algoritmasını belirlemek için 2007 - 2013 yılları arasında bir yarışma düzenlendi. Bu algoritma 224, 256, 384, ve 512 bit uzunluğunda hash çıktısı verir. Açıklaması şöyle

Everything was changed between SHA-2 and SHA-3.

In the specific case of the "length extension attack": the issue is that SHA-2 process data by splitting it into elementary blocks (64 or 128 bytes, depending on the SHA-2 variant), and produces for each block an output which has exactly the same size as the function output. Moreover, the output for a complete message is merely the current output after processing all blocks of the (padded) message. This means that anybody can take a hash output and "continue" processing of a longer message with additional blocks.

In SHA-3, a sponge construction is used. The crucial point is that, in a sponge, the internal state is much larger than the hash function output. Thus, you cannot simply "continue" processing of a message by using a hash output, because that output contains only a fraction of the internal state.