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封榜前rank11最终圆梦省一，感谢队友带飞

Crypto

简单数学题

给了p和q和与差，直接相加相减得到p和q，后面直接解rsa

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from Crypto.Util.number import *
sum_pq = 15870713655456272818998868095126610389501417235762009793315127525027164306871912572802442396878309282140184445917718237547340279497682840149930939938364752
diff_pq = 836877201325346306269647062252443025692393860257609240213263622058769344319275021861627524327674665653956022396760961371531780934904914806513684926008590
e = 65537
c = 24161337439375469726924397660125738582989340535865292626109110404205047138648291988394300469831314677804449487707306159537988907383165388647811395995713768215918986950780552907040433887058197369446944754008620731946047814491450890197003594397567524722975778515304899628035385825818809556412246258855782770070
p=(sum_pq+diff_pq)//2
q=(sum_pq-diff_pq)//2
n=p*q
phi = (p-1)*(q-1)
d = inverse(e, phi)
m = pow(c, d, n)

print(long_to_bytes(m))
#b'DASCTF{ok_1+1_1s_ez_so_try2goldbachs}'

AES

cbc加密，给了key生成方法，密文和iv

md5生成key

Base64

直接大厨解密

brainRSA-1

对于第一个hint可以这样变换

后面可以通过coppersmith解出p

如果m<p，那么mod n和mod p等价，所以后面phi可以用p-1来替代，这样假设能求出flag，但是求不出q无法验证

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from Crypto.Util.number import *

n = 5896603616629976388681343986666930963006582028163928714145532756203237227730274711487003166019427105897965945120232260215410992579837484059292611073419586380525003988344574914431029827063806077732189986757809721088722985286036959879820708133146403409430195581622055470667222891220979774304289695570081825139756219411812254290165809196979501734849253222466549260913814647528326035080523330064602920600175311072318677328858357572118378221037611447468353988765857728693723209366913388728379914720462400719453373674212484217
e = 65537
c = 4221793406745090448159839492516441941495929321499567123472000442699162146372220161860225184236927618558037325910707307459975466187269605134233560519157016842737834824730633694720444565009425747524144994992594172304437752960220406217437575205487944977177237131899857115110278358933279454006801350405232784421011170963118967018535823980784090051685902395650907846245302374549113152846903151411198578675291462184512223571295652757739539096560166939391938607962013244587459259461981764347874215325536867806205636381420076263
h1 = 86682368885754481246073975629273374009118678612781484142142233010648189936701991035424570227832428961089155099087480306450429844896945882196738935354601757929219259054136973233403527177389212490240890908590489235856630191642125591379880282065718229563065862910111151238228617993062409710807546317753676418582796716091984804706084632849079312032895792218093262044435
h2 = 507302396516541130096005191243501282527086130677192353031178107965055262527263846570902262566241833462389458229472609073835612242905629592637875830766904


PR.<x> = PolynomialRing(Zmod(n))
f = x^3 - h1*x^2+x
p = int(f.small_roots(X=2^512,beta=0.4,epsilon=0.01)[1])
print(p)

d = inverse(e,p-1)
m = pow(c,d,p)
print(long_to_bytes(m))
# b'flag{V#@Ry_@ASSy_Pr013L@m-for_RsA!}'

Reverse

你是我的天命人吗

第一个函数是VirtualProtect自解密

第二个函数进入之后创建函数

输入先异或i再转成hex

直接逆向

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s='4440514050437D3E386C3A3F3E6F386D232124202D7420742C2F2E282525782D124344471015405A'
print(len(s))
for i in range(0,len(s),2):
    print(chr(int(s[i:i+2],16)^(i//2)),end="")
#DASCTF{90e042b6b30639a6c464398f22bfd40f}

androidtest

jadx反编译不完全，用jeb打开发现base32的表

so层下存在密文

先base32解密

比赛期间通过测试之后猜测再xor44能得到flag

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a=[0x68 ,0x6d ,0x7f ,0x6f ,0x78 ,0x6a ,0x57 ,0x4d ,0x42 ,0x48 ,0x5e ,0x43 ,0x45 ,0x48 ,0x73 ,0x4d ,0x42 ,0x58 ,0x45 ,0x73 ,0x4d ,0x42 ,0x48 ,0x73 ,0x58 ,0x49 ,0x5f ,0x58 ,0x73 ,0x45 ,0x5f ,0x73 ,0x45 ,0x42 ,0x58 ,0x49 ,0x5e ,0x49 ,0x5f ,0x58 ,0x45 ,0x42 ,0x4b ,0x51]
for i in range(len(a)):
    print(chr(a[i]^44),end="")
#DASCTF{android_anti_and_test_is_interesting}

交叉引用ret_str方法找到关键加密，Onclick里面先执行xor 44再base32加密后和密文比较

Warning-1

输入作为参数传入

调试的时候参数放到parameters里

trace xor

trace cmp

上述trace后得到如下内容

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XOR: 0x31 ^ 0x0 = 0x31
CMP: 0x2e == 0x1
XOR: 0x31 ^ 0x1 = 0x30
CMP: 0x2e == 0x2
XOR: 0x31 ^ 0x2 = 0x33
CMP: 0x2e == 0x3
XOR: 0x31 ^ 0x3 = 0x32
CMP: 0x2e == 0x4
XOR: 0x31 ^ 0x4 = 0x35
CMP: 0x2e == 0x5
XOR: 0x31 ^ 0x5 = 0x34
CMP: 0x2e == 0x6
XOR: 0x31 ^ 0x6 = 0x37
CMP: 0x2e == 0x7
XOR: 0x31 ^ 0x7 = 0x36
CMP: 0x2e == 0x8
XOR: 0x31 ^ 0x8 = 0x39
CMP: 0x2e == 0x9
XOR: 0x31 ^ 0x9 = 0x38
CMP: 0x2e == 0xa
XOR: 0x31 ^ 0xa = 0x3b
CMP: 0x2e == 0xb
XOR: 0x31 ^ 0xb = 0x3a
CMP: 0x2e == 0xc
XOR: 0x31 ^ 0xc = 0x3d
CMP: 0x2e == 0xd
XOR: 0x31 ^ 0xd = 0x3c
CMP: 0x2e == 0xe
XOR: 0x31 ^ 0xe = 0x3f
CMP: 0x2e == 0xf
XOR: 0x31 ^ 0xf = 0x3e
CMP: 0x2e == 0x10
XOR: 0x31 ^ 0x10 = 0x21
CMP: 0x2e == 0x11
XOR: 0x31 ^ 0x11 = 0x20
CMP: 0x2e == 0x12
XOR: 0x31 ^ 0x12 = 0x23
CMP: 0x2e == 0x13
XOR: 0x31 ^ 0x13 = 0x22
CMP: 0x2e == 0x14
XOR: 0x31 ^ 0x14 = 0x25
CMP: 0x2e == 0x15
XOR: 0x31 ^ 0x15 = 0x24
CMP: 0x2e == 0x16
XOR: 0x31 ^ 0x16 = 0x27
CMP: 0x2e == 0x17
XOR: 0x31 ^ 0x17 = 0x26
CMP: 0x2e == 0x18
XOR: 0x31 ^ 0x18 = 0x29
CMP: 0x2e == 0x19
XOR: 0x31 ^ 0x19 = 0x28
CMP: 0x2e == 0x1a
XOR: 0x31 ^ 0x1a = 0x2b
CMP: 0x2e == 0x1b
XOR: 0x31 ^ 0x1b = 0x2a
CMP: 0x2e == 0x1c
XOR: 0x31 ^ 0x1c = 0x2d
CMP: 0x2e == 0x1d
XOR: 0x31 ^ 0x1d = 0x2c
CMP: 0x2e == 0x1e
XOR: 0x31 ^ 0x1e = 0x2f
CMP: 0x2e == 0x1f
XOR: 0x31 ^ 0x1f = 0x2e
CMP: 0x2e == 0x20
XOR: 0x31 ^ 0x20 = 0x11
CMP: 0x2e == 0x21
XOR: 0x31 ^ 0x21 = 0x10
CMP: 0x2e == 0x22
XOR: 0x31 ^ 0x22 = 0x13
CMP: 0x2e == 0x23
XOR: 0x31 ^ 0x23 = 0x12
CMP: 0x2e == 0x24
XOR: 0x31 ^ 0x24 = 0x15
CMP: 0x2e == 0x25
XOR: 0x31 ^ 0x25 = 0x14
CMP: 0x2e == 0x26
XOR: 0x31 ^ 0x26 = 0x17
CMP: 0x2e == 0x27
XOR: 0x31 ^ 0x27 = 0x16
CMP: 0x2e == 0x28
XOR: 0x31 ^ 0x28 = 0x19
CMP: 0x2e == 0x29
XOR: 0x31 ^ 0x29 = 0x18
CMP: 0x2e == 0x2a
XOR: 0x31 ^ 0x2a = 0x1b
CMP: 0x2e == 0x2b
XOR: 0x31 ^ 0x2b = 0x1a
CMP: 0x2e == 0x2c
XOR: 0x31 ^ 0x2c = 0x1d
CMP: 0x2e == 0x2d
XOR: 0x31 ^ 0x2d = 0x1c
CMP: 0x2e == 0x2e
CMP: 0x100 == 0x1
CMP: 0x100 == 0x2
CMP: 0x100 == 0x3
CMP: 0x100 == 0x4
CMP: 0x100 == 0x5
CMP: 0x100 == 0x6
CMP: 0x100 == 0x7
CMP: 0x100 == 0x8
CMP: 0x100 == 0x9
CMP: 0x100 == 0xa
CMP: 0x100 == 0xb
CMP: 0x100 == 0xc
CMP: 0x100 == 0xd
CMP: 0x100 == 0xe
CMP: 0x100 == 0xf
CMP: 0x100 == 0x10
CMP: 0x100 == 0x11
CMP: 0x100 == 0x12
CMP: 0x100 == 0x13
CMP: 0x100 == 0x14
CMP: 0x100 == 0x15
CMP: 0x100 == 0x16
CMP: 0x100 == 0x17
CMP: 0x100 == 0x18
CMP: 0x100 == 0x19
CMP: 0x100 == 0x1a
CMP: 0x100 == 0x1b
CMP: 0x100 == 0x1c
CMP: 0x100 == 0x1d
CMP: 0x100 == 0x1e
CMP: 0x100 == 0x1f
CMP: 0x100 == 0x20
CMP: 0x100 == 0x21
CMP: 0x100 == 0x22
CMP: 0x100 == 0x23
CMP: 0x100 == 0x24
CMP: 0x100 == 0x25
CMP: 0x100 == 0x26
CMP: 0x100 == 0x27
CMP: 0x100 == 0x28
CMP: 0x100 == 0x29
CMP: 0x100 == 0x2a
CMP: 0x100 == 0x2b
CMP: 0x100 == 0x2c
CMP: 0x100 == 0x2d
CMP: 0x100 == 0x2e
CMP: 0x100 == 0x2f
CMP: 0x100 == 0x30
CMP: 0x100 == 0x31
CMP: 0x100 == 0x32
CMP: 0x100 == 0x33
CMP: 0x100 == 0x34
CMP: 0x100 == 0x35
CMP: 0x100 == 0x36
CMP: 0x100 == 0x37
CMP: 0x100 == 0x38
CMP: 0x100 == 0x39
CMP: 0x100 == 0x3a
CMP: 0x100 == 0x3b
CMP: 0x100 == 0x3c
CMP: 0x100 == 0x3d
CMP: 0x100 == 0x3e
CMP: 0x100 == 0x3f
CMP: 0x100 == 0x40
CMP: 0x100 == 0x41
CMP: 0x100 == 0x42
CMP: 0x100 == 0x43
CMP: 0x100 == 0x44
CMP: 0x100 == 0x45
CMP: 0x100 == 0x46
CMP: 0x100 == 0x47
CMP: 0x100 == 0x48
CMP: 0x100 == 0x49
CMP: 0x100 == 0x4a
CMP: 0x100 == 0x4b
CMP: 0x100 == 0x4c
CMP: 0x100 == 0x4d
CMP: 0x100 == 0x4e
CMP: 0x100 == 0x4f
CMP: 0x100 == 0x50
CMP: 0x100 == 0x51
CMP: 0x100 == 0x52
CMP: 0x100 == 0x53
CMP: 0x100 == 0x54
CMP: 0x100 == 0x55
CMP: 0x100 == 0x56
CMP: 0x100 == 0x57
CMP: 0x100 == 0x58
CMP: 0x100 == 0x59
CMP: 0x100 == 0x5a
CMP: 0x100 == 0x5b
CMP: 0x100 == 0x5c
CMP: 0x100 == 0x5d
CMP: 0x100 == 0x5e
CMP: 0x100 == 0x5f
CMP: 0x100 == 0x60
CMP: 0x100 == 0x61
CMP: 0x100 == 0x62
CMP: 0x100 == 0x63
CMP: 0x100 == 0x64
CMP: 0x100 == 0x65
CMP: 0x100 == 0x66
CMP: 0x100 == 0x67
CMP: 0x100 == 0x68
CMP: 0x100 == 0x69
CMP: 0x100 == 0x6a
CMP: 0x100 == 0x6b
CMP: 0x100 == 0x6c
CMP: 0x100 == 0x6d
CMP: 0x100 == 0x6e
CMP: 0x100 == 0x6f
CMP: 0x100 == 0x70
CMP: 0x100 == 0x71
CMP: 0x100 == 0x72
CMP: 0x100 == 0x73
CMP: 0x100 == 0x74
CMP: 0x100 == 0x75
CMP: 0x100 == 0x76
CMP: 0x100 == 0x77
CMP: 0x100 == 0x78
CMP: 0x100 == 0x79
CMP: 0x100 == 0x7a
CMP: 0x100 == 0x7b
CMP: 0x100 == 0x7c
CMP: 0x100 == 0x7d
CMP: 0x100 == 0x7e
CMP: 0x100 == 0x7f
CMP: 0x100 == 0x80
CMP: 0x100 == 0x81
CMP: 0x100 == 0x82
CMP: 0x100 == 0x83
CMP: 0x100 == 0x84
CMP: 0x100 == 0x85
CMP: 0x100 == 0x86
CMP: 0x100 == 0x87
CMP: 0x100 == 0x88
CMP: 0x100 == 0x89
CMP: 0x100 == 0x8a
CMP: 0x100 == 0x8b
CMP: 0x100 == 0x8c
CMP: 0x100 == 0x8d
CMP: 0x100 == 0x8e
CMP: 0x100 == 0x8f
CMP: 0x100 == 0x90
CMP: 0x100 == 0x91
CMP: 0x100 == 0x92
CMP: 0x100 == 0x93
CMP: 0x100 == 0x94
CMP: 0x100 == 0x95
CMP: 0x100 == 0x96
CMP: 0x100 == 0x97
CMP: 0x100 == 0x98
CMP: 0x100 == 0x99
CMP: 0x100 == 0x9a
CMP: 0x100 == 0x9b
CMP: 0x100 == 0x9c
CMP: 0x100 == 0x9d
CMP: 0x100 == 0x9e
CMP: 0x100 == 0x9f
CMP: 0x100 == 0xa0
CMP: 0x100 == 0xa1
CMP: 0x100 == 0xa2
CMP: 0x100 == 0xa3
CMP: 0x100 == 0xa4
CMP: 0x100 == 0xa5
CMP: 0x100 == 0xa6
CMP: 0x100 == 0xa7
CMP: 0x100 == 0xa8
CMP: 0x100 == 0xa9
CMP: 0x100 == 0xaa
CMP: 0x100 == 0xab
CMP: 0x100 == 0xac
CMP: 0x100 == 0xad
CMP: 0x100 == 0xae
CMP: 0x100 == 0xaf
CMP: 0x100 == 0xb0
CMP: 0x100 == 0xb1
CMP: 0x100 == 0xb2
CMP: 0x100 == 0xb3
CMP: 0x100 == 0xb4
CMP: 0x100 == 0xb5
CMP: 0x100 == 0xb6
CMP: 0x100 == 0xb7
CMP: 0x100 == 0xb8
CMP: 0x100 == 0xb9
CMP: 0x100 == 0xba
CMP: 0x100 == 0xbb
CMP: 0x100 == 0xbc
CMP: 0x100 == 0xbd
CMP: 0x100 == 0xbe
CMP: 0x100 == 0xbf
CMP: 0x100 == 0xc0
CMP: 0x100 == 0xc1
CMP: 0x100 == 0xc2
CMP: 0x100 == 0xc3
CMP: 0x100 == 0xc4
CMP: 0x100 == 0xc5
CMP: 0x100 == 0xc6
CMP: 0x100 == 0xc7
CMP: 0x100 == 0xc8
CMP: 0x100 == 0xc9
CMP: 0x100 == 0xca
CMP: 0x100 == 0xcb
CMP: 0x100 == 0xcc
CMP: 0x100 == 0xcd
CMP: 0x100 == 0xce
CMP: 0x100 == 0xcf
CMP: 0x100 == 0xd0
CMP: 0x100 == 0xd1
CMP: 0x100 == 0xd2
CMP: 0x100 == 0xd3
CMP: 0x100 == 0xd4
CMP: 0x100 == 0xd5
CMP: 0x100 == 0xd6
CMP: 0x100 == 0xd7
CMP: 0x100 == 0xd8
CMP: 0x100 == 0xd9
CMP: 0x100 == 0xda
CMP: 0x100 == 0xdb
CMP: 0x100 == 0xdc
CMP: 0x100 == 0xdd
CMP: 0x100 == 0xde
CMP: 0x100 == 0xdf
CMP: 0x100 == 0xe0
CMP: 0x100 == 0xe1
CMP: 0x100 == 0xe2
CMP: 0x100 == 0xe3
CMP: 0x100 == 0xe4
CMP: 0x100 == 0xe5
CMP: 0x100 == 0xe6
CMP: 0x100 == 0xe7
CMP: 0x100 == 0xe8
CMP: 0x100 == 0xe9
CMP: 0x100 == 0xea
CMP: 0x100 == 0xeb
CMP: 0x100 == 0xec
CMP: 0x100 == 0xed
CMP: 0x100 == 0xee
CMP: 0x100 == 0xef
CMP: 0x100 == 0xf0
CMP: 0x100 == 0xf1
CMP: 0x100 == 0xf2
CMP: 0x100 == 0xf3
CMP: 0x100 == 0xf4
CMP: 0x100 == 0xf5
CMP: 0x100 == 0xf6
CMP: 0x100 == 0xf7
CMP: 0x100 == 0xf8
CMP: 0x100 == 0xf9
CMP: 0x100 == 0xfa
CMP: 0x100 == 0xfb
CMP: 0x100 == 0xfc
CMP: 0x100 == 0xfd
CMP: 0x100 == 0xfe
CMP: 0x100 == 0xff
CMP: 0x100 == 0x100
CMP: 0x100 == 0x1
CMP: 0x100 == 0x2
CMP: 0x100 == 0x3
CMP: 0x100 == 0x4
CMP: 0x100 == 0x5
CMP: 0x100 == 0x6
CMP: 0x100 == 0x7
CMP: 0x100 == 0x8
CMP: 0x100 == 0x9
CMP: 0x100 == 0xa
CMP: 0x100 == 0xb
CMP: 0x100 == 0xc
CMP: 0x100 == 0xd
CMP: 0x100 == 0xe
CMP: 0x100 == 0xf
CMP: 0x100 == 0x10
CMP: 0x100 == 0x11
CMP: 0x100 == 0x12
CMP: 0x100 == 0x13
CMP: 0x100 == 0x14
CMP: 0x100 == 0x15
CMP: 0x100 == 0x16
CMP: 0x100 == 0x17
CMP: 0x100 == 0x18
CMP: 0x100 == 0x19
CMP: 0x100 == 0x1a
CMP: 0x100 == 0x1b
CMP: 0x100 == 0x1c
CMP: 0x100 == 0x1d
CMP: 0x100 == 0x1e
CMP: 0x100 == 0x1f
CMP: 0x100 == 0x20
CMP: 0x100 == 0x21
CMP: 0x100 == 0x22
CMP: 0x100 == 0x23
CMP: 0x100 == 0x24
CMP: 0x100 == 0x25
CMP: 0x100 == 0x26
CMP: 0x100 == 0x27
CMP: 0x100 == 0x28
CMP: 0x100 == 0x29
CMP: 0x100 == 0x2a
CMP: 0x100 == 0x2b
CMP: 0x100 == 0x2c
CMP: 0x100 == 0x2d
CMP: 0x100 == 0x2e
CMP: 0x100 == 0x2f
CMP: 0x100 == 0x30
CMP: 0x100 == 0x31
CMP: 0x100 == 0x32
CMP: 0x100 == 0x33
CMP: 0x100 == 0x34
CMP: 0x100 == 0x35
CMP: 0x100 == 0x36
CMP: 0x100 == 0x37
CMP: 0x100 == 0x38
CMP: 0x100 == 0x39
CMP: 0x100 == 0x3a
CMP: 0x100 == 0x3b
CMP: 0x100 == 0x3c
CMP: 0x100 == 0x3d
CMP: 0x100 == 0x3e
CMP: 0x100 == 0x3f
CMP: 0x100 == 0x40
CMP: 0x100 == 0x41
CMP: 0x100 == 0x42
CMP: 0x100 == 0x43
CMP: 0x100 == 0x44
CMP: 0x100 == 0x45
CMP: 0x100 == 0x46
CMP: 0x100 == 0x47
CMP: 0x100 == 0x48
CMP: 0x100 == 0x49
CMP: 0x100 == 0x4a
CMP: 0x100 == 0x4b
CMP: 0x100 == 0x4c
CMP: 0x100 == 0x4d
CMP: 0x100 == 0x4e
CMP: 0x100 == 0x4f
CMP: 0x100 == 0x50
CMP: 0x100 == 0x51
CMP: 0x100 == 0x52
CMP: 0x100 == 0x53
CMP: 0x100 == 0x54
CMP: 0x100 == 0x55
CMP: 0x100 == 0x56
CMP: 0x100 == 0x57
CMP: 0x100 == 0x58
CMP: 0x100 == 0x59
CMP: 0x100 == 0x5a
CMP: 0x100 == 0x5b
CMP: 0x100 == 0x5c
CMP: 0x100 == 0x5d
CMP: 0x100 == 0x5e
CMP: 0x100 == 0x5f
CMP: 0x100 == 0x60
CMP: 0x100 == 0x61
CMP: 0x100 == 0x62
CMP: 0x100 == 0x63
CMP: 0x100 == 0x64
CMP: 0x100 == 0x65
CMP: 0x100 == 0x66
CMP: 0x100 == 0x67
CMP: 0x100 == 0x68
CMP: 0x100 == 0x69
CMP: 0x100 == 0x6a
CMP: 0x100 == 0x6b
CMP: 0x100 == 0x6c
CMP: 0x100 == 0x6d
CMP: 0x100 == 0x6e
CMP: 0x100 == 0x6f
CMP: 0x100 == 0x70
CMP: 0x100 == 0x71
CMP: 0x100 == 0x72
CMP: 0x100 == 0x73
CMP: 0x100 == 0x74
CMP: 0x100 == 0x75
CMP: 0x100 == 0x76
CMP: 0x100 == 0x77
CMP: 0x100 == 0x78
CMP: 0x100 == 0x79
CMP: 0x100 == 0x7a
CMP: 0x100 == 0x7b
CMP: 0x100 == 0x7c
CMP: 0x100 == 0x7d
CMP: 0x100 == 0x7e
CMP: 0x100 == 0x7f
CMP: 0x100 == 0x80
CMP: 0x100 == 0x81
CMP: 0x100 == 0x82
CMP: 0x100 == 0x83
CMP: 0x100 == 0x84
CMP: 0x100 == 0x85
CMP: 0x100 == 0x86
CMP: 0x100 == 0x87
CMP: 0x100 == 0x88
CMP: 0x100 == 0x89
CMP: 0x100 == 0x8a
CMP: 0x100 == 0x8b
CMP: 0x100 == 0x8c
CMP: 0x100 == 0x8d
CMP: 0x100 == 0x8e
CMP: 0x100 == 0x8f
CMP: 0x100 == 0x90
CMP: 0x100 == 0x91
CMP: 0x100 == 0x92
CMP: 0x100 == 0x93
CMP: 0x100 == 0x94
CMP: 0x100 == 0x95
CMP: 0x100 == 0x96
CMP: 0x100 == 0x97
CMP: 0x100 == 0x98
CMP: 0x100 == 0x99
CMP: 0x100 == 0x9a
CMP: 0x100 == 0x9b
CMP: 0x100 == 0x9c
CMP: 0x100 == 0x9d
CMP: 0x100 == 0x9e
CMP: 0x100 == 0x9f
CMP: 0x100 == 0xa0
CMP: 0x100 == 0xa1
CMP: 0x100 == 0xa2
CMP: 0x100 == 0xa3
CMP: 0x100 == 0xa4
CMP: 0x100 == 0xa5
CMP: 0x100 == 0xa6
CMP: 0x100 == 0xa7
CMP: 0x100 == 0xa8
CMP: 0x100 == 0xa9
CMP: 0x100 == 0xaa
CMP: 0x100 == 0xab
CMP: 0x100 == 0xac
CMP: 0x100 == 0xad
CMP: 0x100 == 0xae
CMP: 0x100 == 0xaf
CMP: 0x100 == 0xb0
CMP: 0x100 == 0xb1
CMP: 0x100 == 0xb2
CMP: 0x100 == 0xb3
CMP: 0x100 == 0xb4
CMP: 0x100 == 0xb5
CMP: 0x100 == 0xb6
CMP: 0x100 == 0xb7
CMP: 0x100 == 0xb8
CMP: 0x100 == 0xb9
CMP: 0x100 == 0xba
CMP: 0x100 == 0xbb
CMP: 0x100 == 0xbc
CMP: 0x100 == 0xbd
CMP: 0x100 == 0xbe
CMP: 0x100 == 0xbf
CMP: 0x100 == 0xc0
CMP: 0x100 == 0xc1
CMP: 0x100 == 0xc2
CMP: 0x100 == 0xc3
CMP: 0x100 == 0xc4
CMP: 0x100 == 0xc5
CMP: 0x100 == 0xc6
CMP: 0x100 == 0xc7
CMP: 0x100 == 0xc8
CMP: 0x100 == 0xc9
CMP: 0x100 == 0xca
CMP: 0x100 == 0xcb
CMP: 0x100 == 0xcc
CMP: 0x100 == 0xcd
CMP: 0x100 == 0xce
CMP: 0x100 == 0xcf
CMP: 0x100 == 0xd0
CMP: 0x100 == 0xd1
CMP: 0x100 == 0xd2
CMP: 0x100 == 0xd3
CMP: 0x100 == 0xd4
CMP: 0x100 == 0xd5
CMP: 0x100 == 0xd6
CMP: 0x100 == 0xd7
CMP: 0x100 == 0xd8
CMP: 0x100 == 0xd9
CMP: 0x100 == 0xda
CMP: 0x100 == 0xdb
CMP: 0x100 == 0xdc
CMP: 0x100 == 0xdd
CMP: 0x100 == 0xde
CMP: 0x100 == 0xdf
CMP: 0x100 == 0xe0
CMP: 0x100 == 0xe1
CMP: 0x100 == 0xe2
CMP: 0x100 == 0xe3
CMP: 0x100 == 0xe4
CMP: 0x100 == 0xe5
CMP: 0x100 == 0xe6
CMP: 0x100 == 0xe7
CMP: 0x100 == 0xe8
CMP: 0x100 == 0xe9
CMP: 0x100 == 0xea
CMP: 0x100 == 0xeb
CMP: 0x100 == 0xec
CMP: 0x100 == 0xed
CMP: 0x100 == 0xee
CMP: 0x100 == 0xef
CMP: 0x100 == 0xf0
CMP: 0x100 == 0xf1
CMP: 0x100 == 0xf2
CMP: 0x100 == 0xf3
CMP: 0x100 == 0xf4
CMP: 0x100 == 0xf5
CMP: 0x100 == 0xf6
CMP: 0x100 == 0xf7
CMP: 0x100 == 0xf8
CMP: 0x100 == 0xf9
CMP: 0x100 == 0xfa
CMP: 0x100 == 0xfb
CMP: 0x100 == 0xfc
CMP: 0x100 == 0xfd
CMP: 0x100 == 0xfe
CMP: 0x100 == 0xff
CMP: 0x100 == 0x100
XOR: 0x31 ^ 0x50 = 0x61
CMP: 0x1 == 0x2e
XOR: 0x30 ^ 0x67 = 0x57
CMP: 0x2 == 0x2e
XOR: 0x33 ^ 0x21 = 0x12
CMP: 0x3 == 0x2e
XOR: 0x32 ^ 0x2b = 0x19
CMP: 0x4 == 0x2e
XOR: 0x35 ^ 0xce = 0xfb
CMP: 0x5 == 0x2e
XOR: 0x34 ^ 0xd7 = 0xe3
CMP: 0x6 == 0x2e
XOR: 0x37 ^ 0x84 = 0xb3
CMP: 0x7 == 0x2e
XOR: 0x36 ^ 0x3a = 0xc
CMP: 0x8 == 0x2e
XOR: 0x39 ^ 0xf5 = 0xcc
CMP: 0x9 == 0x2e
XOR: 0x38 ^ 0xc2 = 0xfa
CMP: 0xa == 0x2e
XOR: 0x3b ^ 0xc2 = 0xf9
CMP: 0xb == 0x2e
XOR: 0x3a ^ 0x22 = 0x18
CMP: 0xc == 0x2e
XOR: 0x3d ^ 0x48 = 0x75
CMP: 0xd == 0x2e
XOR: 0x3c ^ 0x1d = 0x21
CMP: 0xe == 0x2e
XOR: 0x3f ^ 0x14 = 0x2b
CMP: 0xf == 0x2e
XOR: 0x3e ^ 0x2a = 0x14
CMP: 0x10 == 0x2e
XOR: 0x21 ^ 0x71 = 0x50
CMP: 0x11 == 0x2e
XOR: 0x20 ^ 0x25 = 0x5
CMP: 0x12 == 0x2e
XOR: 0x23 ^ 0xa7 = 0x84
CMP: 0x13 == 0x2e
XOR: 0x22 ^ 0x73 = 0x51
CMP: 0x14 == 0x2e
XOR: 0x25 ^ 0x3c = 0x19
CMP: 0x15 == 0x2e
XOR: 0x24 ^ 0x9c = 0xb8
CMP: 0x16 == 0x2e
XOR: 0x27 ^ 0x72 = 0x55
CMP: 0x17 == 0x2e
XOR: 0x26 ^ 0xfe = 0xd8
CMP: 0x18 == 0x2e
XOR: 0x29 ^ 0x3c = 0x15
CMP: 0x19 == 0x2e
XOR: 0x28 ^ 0xb7 = 0x9f
CMP: 0x1a == 0x2e
XOR: 0x2b ^ 0xad = 0x86
CMP: 0x1b == 0x2e
XOR: 0x2a ^ 0x80 = 0xaa
CMP: 0x1c == 0x2e
XOR: 0x2d ^ 0xa9 = 0x84
CMP: 0x1d == 0x2e
XOR: 0x2c ^ 0x6f = 0x43
CMP: 0x1e == 0x2e
XOR: 0x2f ^ 0x37 = 0x18
CMP: 0x1f == 0x2e
XOR: 0x2e ^ 0x46 = 0x68
CMP: 0x20 == 0x2e
XOR: 0x11 ^ 0x91 = 0x80
CMP: 0x21 == 0x2e
XOR: 0x10 ^ 0x32 = 0x22
CMP: 0x22 == 0x2e
XOR: 0x13 ^ 0xb4 = 0xa7
CMP: 0x23 == 0x2e
XOR: 0x12 ^ 0xf7 = 0xe5
CMP: 0x24 == 0x2e
XOR: 0x15 ^ 0xa5 = 0xb0
CMP: 0x25 == 0x2e
XOR: 0x14 ^ 0xad = 0xb9
CMP: 0x26 == 0x2e
XOR: 0x17 ^ 0xd8 = 0xcf
CMP: 0x27 == 0x2e
XOR: 0x16 ^ 0x6b = 0x7d
CMP: 0x28 == 0x2e
XOR: 0x19 ^ 0x35 = 0x2c
CMP: 0x29 == 0x2e
XOR: 0x18 ^ 0x8c = 0x94
CMP: 0x2a == 0x2e
XOR: 0x1b ^ 0xe4 = 0xff
CMP: 0x2b == 0x2e
XOR: 0x1a ^ 0x0 = 0x1a
CMP: 0x2c == 0x2e
XOR: 0x1d ^ 0x20 = 0x3d
CMP: 0x2d == 0x2e
XOR: 0x1c ^ 0x2e = 0x32
CMP: 0x2e == 0x2e

两次256轮循环猜测可能是rc4，第一步是把明文xor 下标，然后标准rc4加密

按照思路直接写脚本，发现逆向之后就是flag

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key=[0x50, 0x67, 0x21, 0x2b, 0xce, 0xd7, 0x84, 0x3a, 0xf5, 0xc2,
     0xc2, 0x22, 0x48, 0x1d, 0x14, 0x2a, 0x71, 0x25, 0xa7, 0x73,
     0x3c, 0x9c, 0x72, 0xfe, 0x3c, 0xb7, 0xad, 0x80, 0xa9, 0x6f,
     0x37, 0x46, 0x91, 0x32, 0xb4, 0xf7, 0xa5, 0xad, 0xd8, 0x6b,
     0x35, 0x8c, 0xe4, 0x0, 0x20, 0x2e]

enc=[0x14,0x27,0x70,0x6B,0x9E,0x94,0xF9,0x51,0x8E,0x9F,
     0xB2,0x51,0x69,0x73,0x2F,0x46,0x53,0x5,0xDC,0x36,
     0x69,0xA4,0x3,0x86,0x4B,0xC4,0xC6,0xD5,0xE6,0x5F,
     0x50,0x37,0xF7,0x5C,0xC6,0x86,0xF9,0xA5,0xCA,0x74,
     0x24,0xCC,0xBA,0x7E,0x64,0x7E]

flag=''
for i in range(len(enc)):
    tmp=enc[i]^i^key[i]
    flag+=chr(tmp)
print(flag)
# DASCTF{lsTzx-c5c21iVA-goojqNS-ynFOPRx-489itUh}

正常做法应该写脚本模拟所有操作并trace或者一点点调试，这里小小猜测一手，算是非预期

下面脚本也可以验证加密流程

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def rc4(data, key):
    S = list(range(256))
    j = 0
    out = []

    for i in range(256):
        j = (j + S[i] + key[i % len(key)]) % 256
        S[i], S[j] = S[j], S[i]

    i = j = 0
    for char in data:
        i = (i + 1) % 256
        j = (j + S[i]) % 256
        S[i], S[j] = S[j], S[i]
        out.append(char ^ S[(S[i] + S[j]) % 256])

    return out

key = b'LoveToDeath'
data=bytes([0x14,0x27,0x70,0x6B,0x9E,0x94,0xF9,0x51,0x8E,0x9F,
            0xB2,0x51,0x69,0x73,0x2F,0x46,0x53,0x5,0xDC,0x36,
            0x69,0xA4,0x3,0x86,0x4B,0xC4,0xC6,0xD5,0xE6,0x5F,
            0x50,0x37,0xF7,0x5C,0xC6,0x86,0xF9,0xA5,0xCA,0x74,
            0x24,0xCC,0xBA,0x7E,0x64,0x7E])
decrypted = rc4(data, key)
flag=''
for i in range(len(decrypted)):
    decrypted[i]^=i
    flag+=chr(decrypted[i])
print(flag)
#DASCTF{lsTzx-c5c21iVA-goojqNS-ynFOPRx-489itUh}

既然这样的话我知道大部分人怎么做出来的了，这题看到key和密文长度46，猜一手rc4，然后观察解密后的数据和格式发现还需要异或i直接出，可见CTF解题还是需要一些“巧劲”

信创安全

X1-1

两次解包hap文件得到moudles.abc文件，反编译后找到Index类，发现关键加密

arg0是input，arg1是3*3矩阵，arg2是theSecondKey，arg3是arc4Key

分别进行矩阵加密（输入和arg1），异或，rc4，自定义码表的 base64

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import base64
from Crypto.Cipher import ARC4
import numpy as np

cipher = "37L9UF8uNl1TSgYMLIW/RosGPMxVYXNcUoTTQXihX8ZyaQVgxY9Ywz/0fIwRzI4H"
key2 = bytes([90, 60, 231, 145, 47])
rc4_key = b"HarMonyOS_S3cur3_K3y!2025"

custom_b64 = "3GHIJKLMzxy01245PQRSTUFabcdefghijklmnopqrstuv6789+/NOVWXYZABCDEw"
std_b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
translate_table = str.maketrans(custom_b64, std_b64)


def custom_b64_decode(s):
    std_s = s.translate(translate_table)
    return base64.b64decode(std_s)

def rc4_decrypt(data, key):
    cipher = ARC4.new(key)
    return cipher.decrypt(data)

def xor_decrypt(data, key):
    result = bytearray()
    for i, byte in enumerate(data):
        result.append(byte ^ key[i % len(key)])
    return bytes(result)


def extended_gcd(a, b):
    """扩展欧几里得算法，返回 (gcd, x, y) 使得 ax + by = gcd(a, b)"""
    if a == 0:
        return b, 0, 1
    gcd, x1, y1 = extended_gcd(b % a, a)
    x = y1 - (b // a) * x1
    y = x1
    return gcd, x, y


def mod_inverse(a, m):
    """计算 a 在模 m 下的逆元"""
    gcd, x, _ = extended_gcd(a, m)
    if gcd != 1:
        raise ValueError(f"{a} 在模 {m} 下没有逆元")
    return x % m


def matrix_inverse_mod(matrix, mod=256):
    """计算矩阵在模 mod 下的逆矩阵（使用伴随矩阵法）"""
    n = len(matrix)

    # 计算行列式（模 mod）
    det = int(np.round(np.linalg.det(matrix))) % mod
    if det == 0:
        raise ValueError("矩阵行列式为0，不可逆")

    # 计算行列式的模逆
    det_inv = mod_inverse(det, mod)

    # 计算伴随矩阵
    adj = np.zeros((n, n), dtype=int)

    for i in range(n):
        for j in range(n):
            # 计算代数余子式
            # 删除第i行第j列
            minor = np.delete(np.delete(matrix, i, axis=0), j, axis=1)
            # 计算余子式
            cofactor = (-1) ** (i + j) * int(np.round(np.linalg.det(minor)))
            # 伴随矩阵是代数余子式矩阵的转置
            adj[j][i] = cofactor % mod

    # 计算逆矩阵：伴随矩阵 × 行列式逆元 (模 mod)
    inv_matrix = (adj * det_inv) % mod
    return inv_matrix

def matrix_decrypt(data):
    M = [[1, 2, 3],
         [0, 1, 4],
         [0, 0, 1]]

    inv_M = matrix_inverse_mod(M, 256)

    decrypted = bytearray()
    for i in range(0, len(data), 3):
        block = data[i:i + 3]

        # 矩阵乘法：P = M^{-1} * C (mod 256)
        x, y, z = block
        x_dec = (inv_M[0][0] * x + inv_M[0][1] * y + inv_M[0][2] * z) % 256
        y_dec = (inv_M[1][0] * x + inv_M[1][1] * y + inv_M[1][2] * z) % 256
        z_dec = (inv_M[2][0] * x + inv_M[2][1] * y + inv_M[2][2] * z) % 256
        decrypted.extend([x_dec, y_dec, z_dec])

    return bytes(decrypted)


step1 = custom_b64_decode(cipher)
step2 = rc4_decrypt(step1, rc4_key)
step3 = xor_decrypt(step2, key2)
step4 = matrix_decrypt(step3)
print("flag:",step4)
#DASCTF{H4rmOny0S_Mult1_L4y3r_Crypt0_M4st3r!}

也可以先base64和rc4解密

再进行矩阵运算

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import numpy as np
import binascii
from sympy import Matrix

A = [
    [1, 2, 3],
    [0, 1, 4],
    [0, 0, 1],
]

out = bytearray(binascii.unhexlify("5a3ce7e6671be974c53bc174b8b742cc6e9e62e00547c2fddcf763f889566ed2b8037923d4d3a1ba470813d11c71299a"))

xor_key = [90, 60, 231, 145, 47]

for i in range(len(out)):
    out[i] ^= xor_key[i % len(xor_key)]

n = len(A)

cipther = np.frombuffer(bytes(out), dtype=np.uint8)

inv = Matrix(np.array(A, dtype=int)).inv_mod(256)

out = bytearray()
for block in cipther.reshape(-1, n):#-1 表示自动计算行数
    plain = (inv @ block) % 256
    out.extend(plain.astype(np.uint8))

print(out)

整体逻辑很清晰，就是比赛期间写不出矩阵相关代码🤔

比赛wp
#VM #base32 #矩阵
浙江省省赛2025决赛wp
https://j1ya-22.github.io/2025/11/16/浙江省省赛2025决赛wp/
作者
j1ya
发布于
2025年11月16日
许可协议