# Tag Info

## New answers tagged blowfish

2

The -bf-ecb cipher is expanding the key to 128 bits by zero extending it. The output from -p is the telltale here: $openssl enc -bf-ecb -e -in plaintext.txt -out ciphertext.txt -nosalt -K FFFFFFFFFFFFFFFF -p key=FFFFFFFFFFFFFFFF0000000000000000 Blowfish is defined for 32-448 bit keys, and it appears the OpenSSL implementation chose 128 bits as the size ... 2 You are correct in that after the birthday bound you will leak some plaintext in random 8-byte blocks. Nova's answer has the specifics and links to useful sources. To give you a rough idea of the risk, you can look at what percentage of the data could leak. 10 TB is about$2^{40}$blocks. The expected number of collisions is$2^k (1-(1-2^{-n})^{2^k-1})$, ... 3 I didn't find anything about the exact way Crashplan encrypts files, only that it uses Blowfish in CBC mode. The block size of Blowfish is 64 bit, so there are$2^{64}$different input blocks and the same number of output blocks. All in all$147573953\$ terabytes of different output data. The problem with this is the birthday attack. Summarized it says that ...

2

The same way other ciphers, basically, only it does it better than some. From the Blowfish paper these were the relevant building blocks "demonstrated to produce strong ciphers" in previous designs: "Large S-boxes. Larger S-boxes are more resistant to differential cryptanalysis." "Key-dependent S-boxes. While fixed S-boxes must be designed to be resistant ...

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