Why are my Signature Scripts Different from my professors?

Question

bob_addr = "1NWzVg38ggPoVGAG2VWt6ktdWMaV6S1pJk"#"1FMb8Jnn1jSh7yjDFfonC8xCCH3ittoEzB"
bob_hashed_pubkey = base58check.b58decode(bob_addr)[1:]
bob2_hashed_pubkey = b'\xec\x06\xb2\xbf\x18\xc8\x97\x06\x85_v\x1d!_!\xf31[9\x94'.hex()
bob3_hashed_pubkey =codecs.encode(bob_hashed_pubkey, 'hex')
print("bob_hashed_pubkey: ", bob2_hashed_pubkey )

bob_private_key = "CF933A6C602069F1CBC85990DF087714D7E86DF0D0E48398B7D8953E1F03534A"

prv_txid = "84d813beb51c3a12cb5d0bb18c6c15062453d476de24cb2f943ca6e20115d85c"

charlie_addr = "17X4s8JdSdLxFyraNUDBzgmnSNeZpjm42g"
charlie_hashed_pubkey = base58check.b58decode(charlie_addr)[1:]
charlie2_hashed_pubkey = b'G\x80u\x92*\xf4\x1f\xb4A\xaa\n\xb6~\x91\xae\xf2~\xf1\xe6\x86'.hex()

class raw_tx:
    version        = struct.pack("<L", 1)
    tx_in_count    = struct.pack("<B", 1)
    tx_in          = {}
    tx_out_count   = struct.pack("<B", 2)
    tx_out1         = {}
    tx_out2         = {}
    lock_time      = struct.pack("<L", 0)
    hashcode       = struct.pack("<L", 1)
    nonce          = struct.pack("Q", 0)

class raw_tx2:
    version        = struct.pack("<L", 1)
    lock_time      = struct.pack("<L", 0)
    hashcode       = struct.pack("<L", 1)

def flip_byte_order(string):
    flipped = "".join(reversed([string[i:i+2] for i in range(0, len(string), 2)]))
    return flipped

rtx    = raw_tx()

rtx.tx_in["txouthash"]   = codecs.decode(flip_byte_order(prv_txid), 'hex')
rtx.tx_in["tx_out_index"] = struct.pack("<L", 0)
rtx.tx_in["script"]      = codecs.decode(("76a914%s88ac" % bob2_hashed_pubkey), 'hex')
rtx.tx_in["script_bytes"]= struct.pack("<B", len(rtx.tx_in["script"]))
rtx.tx_in["sequence"]     = codecs.decode("ffffffff", 'hex')
rtx.tx_out1["value"]           = struct.pack("<Q", 100000)
rtx.tx_out1["pk_script"]       = codecs.decode(("76a914%s88ac" % charlie2_hashed_pubkey), 'hex')
rtx.tx_out1["pk_script_bytes"] = struct.pack("<B", len(rtx.tx_out1["pk_script"]))
rtx.tx_out2["value"]           = struct.pack("<Q", 50000)
rtx.tx_out2["pk_script"]       = codecs.decode(("76a914%s88ac" % bob2_hashed_pubkey), 'hex')
rtx.tx_out2["pk_script_bytes"] = struct.pack("<B", len(rtx.tx_out2["pk_script"]))

raw_tx_string = (

    rtx.version +
    rtx.tx_in_count +
    rtx.tx_in["txouthash"] +
    rtx.tx_in["tx_out_index"]+
    rtx.tx_in["script_bytes"]+
    rtx.tx_in["script"] +
    rtx.tx_in["sequence"]+
    rtx.tx_out_count +
    rtx.tx_out1["value"]+
    rtx.tx_out1["pk_script_bytes"]+
    rtx.tx_out1["pk_script"]+
    rtx.tx_out2["value"]+
    rtx.tx_out2["pk_script_bytes"]+
    rtx.tx_out2["pk_script"]+
    rtx.lock_time +
    struct.pack("<L", 1)  

)

hashed_tx_to_sign = hashlib.sha256(hashlib.sha256(raw_tx_string).digest()).digest()
sk = ecdsa.SigningKey.from_string(codecs.decode(bob_private_key, 'hex'), curve = ecdsa.SECP256k1)
vk = sk.verifying_key
public_key = (b'\04'.hex() + vk.to_string().hex())
signature = sk.sign_digest(hashed_tx_to_sign, sigencode=ecdsa.util.sigencode_der)
sigscript = (
     signature
     + b'\01' 
     + struct.pack("<B", len(codecs.decode(public_key, 'hex')))
     + codecs.decode(public_key, 'hex')

    )
print("public_key: ", public_key)
ha  = rtx.version.hex()
ha1 = rtx.tx_in_count.hex()
ha2 = flip_byte_order(prv_txid)
ha3 = struct.pack("<L", 0).hex()
ha4 = struct.pack("<B", len(sigscript) + 1).hex()
ha40 = struct.pack("<B", len(signature) + 1).hex()
ha5 = sigscript.hex()
ha6 = 'ffffffff'
ha7 = rtx.tx_out_count.hex()
ha8 = struct.pack("<Q", 100000).hex()
ha9 = struct.pack("<B", len(rtx.tx_out1["pk_script"])).hex()
ha10 = ('76a914%s88ac' % charlie2_hashed_pubkey)
ha11 = struct.pack("<Q", 50000).hex()
ha12 = struct.pack("<B", len(rtx.tx_out2["pk_script"])).hex()
ha13 = ('76a914%s88ac' % bob2_hashed_pubkey)
ha14 = rtx.lock_time.hex()

my output is :

01000000
01
5cd81501e2a63c942fcb24de76d4532406156c8cb10b5dcb123a1cb5be13d884
00000000
8b
48
304502207088158730ae6a7f0d6bc51e3e6ea30fb36599a5017760f222f20dee8a4d6701022100ff1636de2d06332e78532bcb8cfcb15db4bd956bd53bbe98ace82d1c2f6b9c2b014
10437078f8c4a54b67cd1724a3535cb1918bca186c7a143459c9aac35113d4a958b0d4eea6b320fa82c17147b72e0fe11c08b0054897ffb7bdb194f259b0db9e129
ffffffff
02
a086010000000000
1976a914478075922af41fb441aa0ab67e91aef27ef1e68688ac
50c3000000000000
1976a914ec06b2bf18c89706855f761d215f21f3315b399488ac
00000000

her output is:

01000000
01
5cd81501e2a63c942fcb24de76d4532406156c8cb10b5dcb123a1cb5be13d884
00000000
8b
48
304502205139475c3a1b5d6c009d1856fcc906a50e594eac92e317e989fec0fd2a1f73b8022100d36ba3cc952ef0e71df0b6f0215cdc7136e90ce6134cd21245645bbc7b63bc6a01410437078f8c4a54b67cd1724a3535cb1918bca186c7a143459c9aac35113d4a958b0d4eea6b320fa82c17147b72e0fe11c08b0054897ffb7bdb194f259b0db9e129
ffffffff
02
a086010000000000
19
76a914478075922af41fb441aa0ab67e91aef27ef1e68688ac
50c3000000000000
19
76a914ec06b2bf18c89706855f761d215f21f3315b399488ac
00000000

Can one let me know why my signature script is a not identical?

Answer 1

ECDSA signing is not deterministic. A random number k "nonce" is used for signing, and a different nonce must be used for every signature made with the same private key. (Otherwise, the private key could be extracted by a 3rd person.) This could be a random number, as it's in your case. However, never systems generate nonce deterministically, usually using RFC 6979.

Returning back to your question, both signatures are valid. Just make sure you don't publish both transactions. If you do, the network will just ignore one of the transactions as a double-spend, and it won't have any important consequences.

Answer 2

Signing the same piece of data with the same key typically produces different signatures unless you are using a deterministic signature scheme. Check if that is the case with the library you are using for signing.

EDIT: Seems like python-ecdsa supports deterministic signatures