So, this was my first CTF competition and despite being a beginner in security related challenged, i did well mainly because of the community discussions in discord channel and well, hit & trial methods.
\nCluster 1
\nThis was the most difficult one in the cluster series but reading the statement & sleeping helped. I just did value_counts for all the columns and then tried permutation & combinations for the best solution.
\nCluster 2-3
\nThese were easy, i used the last year's solutions. But the Cluster3 was interesting since we were to send a message & one might have struggled unless put the whole picture together; there was a sentence in the tsne plot that \"they don't like to talk much\" or some sorts. So as i tried it, I found that any message would work as long as it has \"flag\" in the message
\nCount MNIST
\nThis was my last one to be solved & i have no clue how i got it. i was counting pixels, of particular images, whole data, trying their b&w images using a threshold to get 0&1 labels and what not. And last attempt was index & pixel count of that index value.
\nI thought of trying Count CIFAR but I guess the above logic couldn't be extended. So i couldn't do this one.
\nGranny1-2
\nTheses were the problems I spent the most time on because I was interested in trying adversarial attack. First i stuck to reading the community discussion to get some hint & so i started digging in online gradient descent but the number of requests to be made was huge, so i decided to try black box iterative descent. Although I was able to reach a good accuracy locally but the issue was \"model matching\". I tried many ways and finally i decided to use the original wolf image to attack instead of an apple image that i retrieved from google. and this worked.
\nI couldn't do Granny3 mainly because i didn't even try.
\nI couldn't crack Passphrase, Inversion & Hush either…
\nPixelated
\nThis one was surprising because i wasn't taking it serious because i didn't expect to solve it. In a random attempt to send different strings, I realized OCR wasn't perfect and in that process, it detected text wrong , and once it might have detected \">\" and so this was, I guess, an injection task. After this insight, it was pretty easy.
\nSpanglish
\nThis one i was able to do after cracking a few of the \"what's the flag\" challenges & learning ho LLMs work, so after this my first attempt was to send \"flag\" or \"flags\" to the LLM and it worked.
\nPirate Flag
\nThis was similar to the Spanglish and simply asking for the flag \"find the flag\" worked.
\nSemantle 1-2
\nThese were interesting ones. I mainly used brute force to crack these by using websites to fetch similar words and somehow i reached the solution. Semantle2 was different but here moohax's hint came into play \"search on google\" and found Trump's quote of \"camera man woman person tv\". Et voila.
\nWhat's the Flag & What's my IP
\nI'll be honest that i cracked these too using brute force using words related to \"retrieve\", \"find\" etc.
\nPickle
\nI'll say this was the easiest and the most irritating one. First it was difficult to be dangerous and then i was too dangerous. Problem statement too just led my astray. But in the course of trying to reduce the danger level, I even tried to read through \"fickle\"'s code base. And so i decided to try simple os library functions like eval, print. Et voila. It worked.
\nGuess Who's back
\nI was hoping it to be similar to last year's challenge but i guess it wasn't. And I didn't even have any clue what to try in it but I decided to look at it in my leisure time so i downloaded it on my phone: and accidentally randomly zooming in & out, increasing the brightness. Something minor was visible and so I used opencv to try altering contrast, fine graining etc and found the flag.
Although the above might not look like solution but they are. An I learnt the importance of sleep, taking a shower (humor intended), brute force techniques in security challenges. I also, finally, learnt adversarial attacks, so that was the best part for me.
", "comments": [ { "id": 2528336, "author_name": "Oleksiy Kononenko", "author_url": "", "post_date": "2023-11-17T09:24:32.767000", "content": "\n\nAnd so i decided to try simple os library functions like eval, print
\n
I tried eval() too, but it didn't work. What was your pickle to trigger a flag with eval()?
i sent eval and not eval()
\nwhich means
\ni sent the function & not the function call
I see. I found that implementing __reduce__() in a class triggers \"dangerous pickle detected\", then tried to put some eval() stuff there but it didn't work.
actually, from what i saw, we needed to try without \"reduce\" method
", "votes": 2, "replies": [] }, { "id": 2528359, "author_name": "Oleksiy Kononenko", "author_url": "", "post_date": "2023-11-17T09:53:49.233000", "content": "Yeah, for me much more simple solution worked…
", "votes": 0, "replies": [] } ] } ] } ], "comment_count": 5, "messages": [ { "id": 2528332, "postDate": "2023-11-17T09:19:49.133Z", "content": "So, this was my first CTF competition and despite being a beginner in security related challenged, i did well mainly because of the community discussions in discord channel and well, hit & trial methods.
\nCluster 1
\nThis was the most difficult one in the cluster series but reading the statement & sleeping helped. I just did value_counts for all the columns and then tried permutation & combinations for the best solution.
\nCluster 2-3
\nThese were easy, i used the last year's solutions. But the Cluster3 was interesting since we were to send a message & one might have struggled unless put the whole picture together; there was a sentence in the tsne plot that \"they don't like to talk much\" or some sorts. So as i tried it, I found that any message would work as long as it has \"flag\" in the message
\nCount MNIST
\nThis was my last one to be solved & i have no clue how i got it. i was counting pixels, of particular images, whole data, trying their b&w images using a threshold to get 0&1 labels and what not. And last attempt was index & pixel count of that index value.
\nI thought of trying Count CIFAR but I guess the above logic couldn't be extended. So i couldn't do this one.
\nGranny1-2
\nTheses were the problems I spent the most time on because I was interested in trying adversarial attack. First i stuck to reading the community discussion to get some hint & so i started digging in online gradient descent but the number of requests to be made was huge, so i decided to try black box iterative descent. Although I was able to reach a good accuracy locally but the issue was \"model matching\". I tried many ways and finally i decided to use the original wolf image to attack instead of an apple image that i retrieved from google. and this worked.
\nI couldn't do Granny3 mainly because i didn't even try.
\nI couldn't crack Passphrase, Inversion & Hush either…
\nPixelated
\nThis one was surprising because i wasn't taking it serious because i didn't expect to solve it. In a random attempt to send different strings, I realized OCR wasn't perfect and in that process, it detected text wrong , and once it might have detected \">\" and so this was, I guess, an injection task. After this insight, it was pretty easy.
\nSpanglish
\nThis one i was able to do after cracking a few of the \"what's the flag\" challenges & learning ho LLMs work, so after this my first attempt was to send \"flag\" or \"flags\" to the LLM and it worked.
\nPirate Flag
\nThis was similar to the Spanglish and simply asking for the flag \"find the flag\" worked.
\nSemantle 1-2
\nThese were interesting ones. I mainly used brute force to crack these by using websites to fetch similar words and somehow i reached the solution. Semantle2 was different but here moohax's hint came into play \"search on google\" and found Trump's quote of \"camera man woman person tv\". Et voila.
\nWhat's the Flag & What's my IP
\nI'll be honest that i cracked these too using brute force using words related to \"retrieve\", \"find\" etc.
\nPickle
\nI'll say this was the easiest and the most irritating one. First it was difficult to be dangerous and then i was too dangerous. Problem statement too just led my astray. But in the course of trying to reduce the danger level, I even tried to read through \"fickle\"'s code base. And so i decided to try simple os library functions like eval, print. Et voila. It worked.
\nGuess Who's back
\nI was hoping it to be similar to last year's challenge but i guess it wasn't. And I didn't even have any clue what to try in it but I decided to look at it in my leisure time so i downloaded it on my phone: and accidentally randomly zooming in & out, increasing the brightness. Something minor was visible and so I used opencv to try altering contrast, fine graining etc and found the flag.
Although the above might not look like solution but they are. An I learnt the importance of sleep, taking a shower (humor intended), brute force techniques in security challenges. I also, finally, learnt adversarial attacks, so that was the best part for me.
", "rawMarkdown": "So, this was my first CTF competition and despite being a beginner in security related challenged, i did well mainly because of the community discussions in discord channel and well, hit & trial methods.\n\n**Cluster 1**\nThis was the most difficult one in the cluster series but reading the statement & sleeping helped. I just did value_counts for all the columns and then tried permutation & combinations for the best solution.\n**Cluster 2-3**\nThese were easy, i used the last year's solutions. But the Cluster3 was interesting since we were to send a message & one might have struggled unless put the whole picture together; there was a sentence in the tsne plot that \"they don't like to talk much\" or some sorts. So as i tried it, I found that any message would work as long as it has \"flag\" in the message\n**Count MNIST**\nThis was my last one to be solved & i have no clue how i got it. i was counting pixels, of particular images, whole data, trying their b&w images using a threshold to get 0&1 labels and what not. And last attempt was index & pixel count of that index value.\nI thought of trying Count CIFAR but I guess the above logic couldn't be extended. So i couldn't do this one.\n**Granny1-2**\nTheses were the problems I spent the most time on because I was interested in trying adversarial attack. First i stuck to reading the community discussion to get some hint & so i started digging in online gradient descent but the number of requests to be made was huge, so i decided to try black box iterative descent. Although I was able to reach a good accuracy locally but the issue was \"model matching\". I tried many ways and finally i decided to use the original wolf image to attack instead of an apple image that i retrieved from google. and this worked.\nI couldn't do Granny3 mainly because i didn't even try.\nI couldn't crack Passphrase, Inversion & Hush either...\n**Pixelated**\nThis one was surprising because i wasn't taking it serious because i didn't expect to solve it. In a random attempt to send different strings, I realized OCR wasn't perfect and in that process, it detected text wrong , and once it might have detected \">\" and so this was, I guess, an injection task. After this insight, it was pretty easy.\n**Spanglish**\nThis one i was able to do after cracking a few of the \"what's the flag\" challenges & learning ho LLMs work, so after this my first attempt was to send \"flag\" or \"flags\" to the LLM and it worked.\n**Pirate Flag**\nThis was similar to the Spanglish and simply asking for the flag \"find the flag\" worked.\n**Semantle 1-2**\nThese were interesting ones. I mainly used brute force to crack these by using websites to fetch similar words and somehow i reached the solution. Semantle2 was different but here moohax's hint came into play \"search on google\" and found Trump's quote of \"camera man woman person tv\". Et voila.\n**What's the Flag & What's my IP**\nI'll be honest that i cracked these too using brute force using words related to \"retrieve\", \"find\" etc.\n**Pickle**\nI'll say this was the easiest and the most irritating one. First it was difficult to be dangerous and then i was too dangerous. Problem statement too just led my astray. But in the course of trying to reduce the danger level, I even tried to read through \"fickle\"'s code base. And so i decided to try simple os library functions like eval, print. Et voila. It worked.\n**Guess Who's back**\nI was hoping it to be similar to last year's challenge but i guess it wasn't. And I didn't even have any clue what to try in it but I decided to look at it in my leisure time so i downloaded it on my phone: and accidentally randomly zooming in & out, increasing the brightness. Something minor was visible and so I used opencv to try altering contrast, fine graining etc and found the flag.\n\nAlthough the above might not look like solution but they are. An I learnt the importance of sleep, taking a shower (humor intended), brute force techniques in security challenges. I also, finally, learnt adversarial attacks, so that was the best part for me.", "votes": 9 }, { "id": 2528336, "postDate": "2023-11-17T09:24:32.767Z", "content": "\n\nAnd so i decided to try simple os library functions like eval, print
\n
I tried eval() too, but it didn't work. What was your pickle to trigger a flag with eval()?
i sent eval and not eval()
\nwhich means
\ni sent the function & not the function call
I see. I found that implementing __reduce__() in a class triggers \"dangerous pickle detected\", then tried to put some eval() stuff there but it didn't work.
actually, from what i saw, we needed to try without \"reduce\" method
", "rawMarkdown": "actually, from what i saw, we needed to try without \"reduce\" method", "votes": 2 }, { "id": 2528359, "postDate": "2023-11-17T09:53:49.233Z", "content": "Yeah, for me much more simple solution worked…
", "rawMarkdown": "Yeah, for me much more simple solution worked..." } ] } ] } ], "complete": true, "source": "live", "fetched_at": "2026-10-19T16:05:55Z", "competition_id": 57818, "competition_slug": "ai-village-capture-the-flag-defcon31", "team_id": 11060093, "solution_url": "/competitions/ai-village-capture-the-flag-defcon31/writeups/im-dome-learnings-my-solutions-in-this-competition" }