This commit is contained in:
aaron
2021-12-04 05:22:26 +01:00
parent f5e3af5326
commit 97dd63e956

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@@ -17,7 +17,7 @@ HTB{4ff1n3_c1ph3r_15_51mpl3_m47h5}
- It's a known plaintext attack. - It's a known plaintext attack.
- The encryption works by applying `(a*byte+b)%n` for each byte of the pdf. - The encryption works by applying `(a*byte+b)%n` for each byte of the pdf.
- Where `a` and `b` remain static across the whole file. - Where `a` and `b` remain static during the entire encryption process.
- The PDFv5 Header is known (`00000000: 2550 4446 2d31 2e35 0a25 e2e3 cfd3 0a37 %PDF-1.5.%.....7`) - The PDFv5 Header is known (`00000000: 2550 4446 2d31 2e35 0a25 e2e3 cfd3 0a37 %PDF-1.5.%.....7`)
- Constraint 1: Factor `a` has to be a number between 1..256 while not sharing a common divisor with 256 - Constraint 1: Factor `a` has to be a number between 1..256 while not sharing a common divisor with 256
- Constraitn 2: Factor `b` has to be a number between 1..256 - Constraitn 2: Factor `b` has to be a number between 1..256