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spake / crypto100.md
Created September 27, 2015 14:53
Trend Micro CTF 2015: Crypto 100

We get two pieces of information; what looks like an RSA public key:

-----BEGIN PUBLIC KEY-----
MDwwDQYJKoZIhvcNAQEBBQADKwAwKAIhALYtzp8lgWNXI9trGI8S8EacvuDLxdrL
NsNuDJa26nv8AgMBAAE=
-----END PUBLIC KEY-----

and what appears to be an encrypted message:

kPmDFLk5b/torG53sThWwEeNm0AIpEQek0rVG3vCttc=
@spake
spake / crypto400.md
Last active October 23, 2015 08:51
Trend Micro CTF 2015: Crypto 400

We get a single file, document.xbm, which looks like an XBM image (a strange old file format that encodes images inside C strings). In our case, we have three arrays of bytes: bits, metadata1, and metadata2.

#define ________________width 1024
#define ________________height 540

static unsigned char ________________bits[] =
{
  0xD0, 0xCF, 0x11, 0xE0, 0xA1, 0xB1, 0x1A, 0xE1, 0x00, 0x00,
 ...
### Keybase proof
I hereby claim:
* I am spake on github.
* I am spake (https://keybase.io/spake) on keybase.
* I have a public key whose fingerprint is E197 3833 6C4A 003B EBD3 FF81 5E60 794F 76D6 6371
To claim this, I am signing this object: