p = F7E75FDC469067FFDC4E847C51F452DF
q = E85CED54AF57E53E092113E62F436F4F
e = 0D88C3
3.2 Task 2: Encrypting a Message
Let (e, n) be the public key. Please encrypt the message "A top secret!" (the quotations are not
included). We need to convert this ASCII string to a hex string, and then convert the hex string to a BIGNUM
using the hex-to-bn API BN hex2bn(). The following python command can be used to convert a plain
ASCII string to a hex string.
SEED Labs – RSA Public-Key Encryption and Signature Lab 5
$ python -c ’print("A top secret!".encode("hex"))’
4120746f702073656372657421
The public keys are listed in the followings (hexadecimal). We also provide the private key d to help
you verify your encryption result.
n = DCBFFE3E51F62E09CE7032E2677A78946A849DC4CDDE3A4D0CB81629242FB1A5
e = 010001 (this hex value equals to decimal 65537)
M = A top secret!
d = 74D806F9F3A62BAE331FFE3F0A68AFE35B3D2E4794148AACBC26AA381CD7D30D
3.3 Task 3: Decrypting a Message
The public/private keys used in this task are the same as the ones used in Task 2. Please decrypt the following
ciphertext C, and convert it back to a plain ASCII string.
C = 8C0F971DF2F3672B28811407E2DABBE1DA0FEBBBDFC7DCB67396567EA1E2493F
You can use the following python command to convert a hex string back to to a plain ASCII string.
$ python -c ’print("4120746f702073656372657421".decode("hex"))’
A top secret!
3.4 Task 4: Signing a Message
The public/private keys used in this task are the same as the ones used in Task 2. Please generate a signature
for the following message (please directly sign this message, instead of signing its hash value):
M = I owe you $2000.
Please make a slight change to the message M, such as changing $2000 to $3000, and sign the modified
message. Compare both signatures and describe what you observe.
3.5 Task 5: Verifying a Signature
Bob receives a message M = "Launch a missile." from Alice, with her signature S. We know that
Alice’s public key is (e, n). Please verify whether the signature is indeed Alice’s or not. The public key
and signature (hexadecimal) are listed in the following:
M = Launch a missle.
S = 643D6F34902D9C7EC90CB0B2BCA36C47FA37165C0005CAB026C0542CBDB6802F
e = 010001 (this hex value equals to decimal 65537)
n = AE1CD4DC432798D933779FBD46C6E1247F0CF1233595113AA51B450F18116115