[erlang-questions] Crypto Library Truncates the last bytes of ciphertext

[Shobhit Singh]

This is already fixed, please ignore. This is fixed on the c side by adding
padding equals to 0. Thanks

On Fri, Jun 23, 2017 at 11:14 AM, Shobhit Singh <shobhitpratap1@REDACTED>
wrote:

> Hi All,
>
> I am facing a problem with encrypting AES 256 bit CBC in Erlang and then
> decrypting it in c code. Whereas Encryption/decryption works in Erlang and
> C but not from one to another.
>
> the same data I Encrypted and decrypted in C and then made a Hex dump. The
> actual Encrypted data Erlang is senginh is 128 Bytes and the same data
> Encrypted by C openssl library is 144 bytes. That's normal cipher text are
> usually long. Here's the output
>
> This is send by Erlang
>
>     Encrypted =  128
>
> a5 ab d0 68 18 61 ad 82 b1 63 32 16 33 b4 70 7b  24 12 d0 aa fa 83 c3 a2 b6 a2 fd 0e 79 f2 3d 3c
> ca ac 4a 79 df 32 80 ff 86 33 fd 5b c3 ae 5a 5d 4d 41 01 73 77 40 19 83 2f f5 44 9c a3 91 6f 7d 8f d0 ff 35 83 dc ae f3 40 78 e5 15 56 6b 8b 94
> a4 27 90 6a e8 40 fc ea 1a d0 8a bb d5 f4 d2 0b
> ae 2f 7e 04 61 b3 c2 55 08 cf 74 8c ec 03 91 d15f 6a 24 79 f1 e4 99 78 e2 7d e3 8a 82 b7 d9 27
>
> This is Output of Openssl (c) library fof the same data.
>
> Encrypted = 144
>
> a5 ab d0 68 18 61 ad 82 b1 63 32 16 33 b4 70 7b  24 12 d0 aa fa 83 c3 a2 b6 a2 fd 0e 79 f2 3d 3c
> ca ac 4a 79 df 32 80 ff 86 33 fd 5b c3 ae 5a 5d 4d 41 01 73 77 40 19 83 2f f5 44 9c a3 91 6f 7d 8f d0 ff 35 83 dc ae f3 40 78 e5 15 56 6b 8b 94
> a4 27 90 6a e8 40 fc ea 1a d0 8a bb d5 f4 d2 0b
> ae 2f 7e 04 61 b3 c2 55 08 cf 74 8c ec 03 91 d1 5f 6a 24 79 f1 e4 99 78 e2 7d e3 8a 82 b7 d9 27
> f7 01 c0 ed 95 e3 14 e5 d2 62 21 da a9 1d 2a e7
>
> The last 16 bytes are missing from Erlang. Is there any other API I need
> to call from Erlang Crypto library.
>
>
> Erlang Code:
>
> Ivec = "1200000000000000",Key = "586E36EEE726B37F70A6F7B770764E99",Data = "encrypt[38ce517c95b011bbfc999f36d09e4feb92d22dd8,38ce517c95b011bbfc999f36d09e4feb92d22222]",PaddedText = string:left(Data ++ ",",128,$0),%%Data is "encrypt[38ce517c95b011bbfc999f36d09e4feb92d22dd8,38ce517c95b011bbfc999f36d09e4feb92d22222],0000000000000000000000000000000000000"EncryptedText = crypto:block_encrypt(aes_cbc256, Key, Ivec, PaddedText),%%Send to C code
>
>
> Thanks,
> Shobhit
>
>
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