cryptoProeasy

Sign Easy

spbctf

Task: RSA signature oracle where you need to sign message 2000 but can only request signatures for other messages. Solution: Exploit RSA multiplicative homomorphism by getting signatures for 2 and 1000, then multiplying them to forge signature for 2000.

$ ls tags/ techniques/
rsadigital_signaturehomomorphic
signature_forgeryrsa_multiplicative_homomorphism
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