Digital Face Manipulations: Types, Techniques and Countermeasures

From Antispoofing Wiki

Digital face manipulation has recently emerged as a significant threat to biometric systems. Although manipulation of images/photographs — photoshopping — has been a popular practice for many years, video manipulation has been relatively unknown. Video manipulation became possible after the introduction of the video deepfakes. The deepfake technology has been in development since 1990s with Video Rewrite being the first tool of its kind. This program could alter the lip movement of a person in a video, so it would realistically match a completely different audio track. But it was not until 2017 when deepfakes became a global phenomenon. Using tools like MelNet, Wombo, Adobe Voco or Face Swap Live, even amateur users can produce believable face and voice manipulations.



Experts predict that fabricated materials using digital face manipulation can be used for disinformation, fraud, reputational damage, discrediting legitimate proofs (reality apathy and liar’s dividend), and terrorism etc.

In one instance, deepfake allegations were used as a pretext for a failed coup d’etat in Gabon. A video in question containing the president’s speech was used by the country’s military to spawn rumors and hysteria among the people.


Digital Face Manipulation

Digital face manipulation is a technique, which allows altering biometric/anatomical properties of the face or creating a new face from scratch using specialized digital tools. These tools can vary from mainstream applications like FaceApp or MyHeritage to sophisticated neural networks.


Types of Face Manipulation

Currently, there exist 6 principal types of face manipulation.

Entire Face Synthesis


Face synthesis technology is capable of modeling a fake and nonexistent face from scratch. This method puts to work two “competing” neural networks and by working in tandem, they form a Generative Adversarial Network — GAN. The first network is called Generator G: it is responsible for distributing and creating new visual samples. Its counterpart is called Discriminator D and its purpose is to assess whether the visual sample comes from the genuine training data and is not fake. As a result, such a GAN can produce highly believable results. A GAN may use databases with up to 10K Faces, as its primary source of samples.

Identity Swap

This technique involves replacing a person’s original face (source) with the face of a different person (target). Face swapping can be done using tools such as DeepFaceLab, Face Swap Live or ZAO — most of which are freely available and do not require any programming skills. These apps achieve a face swap through a complex algorithm. It includes face detection/cropping, extraction, new face synthesis and the final blending. The last stage subtly mixes the “extracted” face with the source video.

Morphed Face

This method basically morphs two different faces into a new one, which retains biometric characteristics of both at the same time. Morphing can often use multiple faces to create a final morphed image. Consequently, a morphed face can potentially be successful at passing verification as one or more individuals. As a result, it poses a serious threat to facial recognition systems: from their efficacy to public reputation.

Face morphing typically includes three stages:

  • Likeness. It determines the likeness between face images of the different people: eyes, lips, nose, nasolabial folds, etc.
  • Distortion. It creates geometric alignment of the facial features “borrowed’ from different personas.
  • Color blending. The color values of the multiple images in use are carefully blended together.

Morphing, however, is mostly used for static images, rather than videos.

Attribute Manipulation

This technique is also called “face retouching”, as it involves manipulation of facial attributes. Attribute manipulation is capable of altering a certain facial element: hair, eye color, skin texture, and so on. FaceApp is the most commonly known attribute manipulation tool. This method also employs GAN, particularly the Invertible Conditional GAN (IcGAN). In this case, an encoder works in unison with a conditional GAN, providing a high-level attribute manipulation.


Attribute manipulation has become popular with the rise of FaceApp
Attribute manipulation has become popular with the rise of FaceApp

Expression Swap

Expression swap, also known as face reenactment, basically “puts” one person’s facial expression on the face of another person. Emotions such as smiling, frowning, smirking, etc. can be manipulated and tweaked with the help of expression swap. This method employs various tools including GANs, Neural Textures and Face2Face. In essence, they all perform the same function: extracting the source expression and transferring it to the target footage, while also retaining the target’s identity.

Another technique of expression swap uses Neural Textures which utilize the original video data to learn a neural texture of the target subject.



Audio-to-Video & Text-to-Video

Audio-to-video and text-to-video methods are based on the same principles as the first known deepfake tool Video Rewrite. Converting audio and text data to speech is possible when a recurrent neural network equipped with Long Short-Term Memory (LSTM) is employed. Basically it analyzes the audio wave to learn which vowels/consonants are uttered by the speaker. It then provides an accurate mapping of the mouth shapes, as well as correct lip movement tempo. Moreover, a conditional recurrent generation network is capable of producing realistic facial expressions and head movement.

Examples







Mitigating Digital Face Manipulations

Digital face manipulation can be detected and mitigated using techniques proposed by experts and researchers. However, no technique has yet been able to provide a 100% failproof detection results.

Detection Using Multiple Data Modalities

Multiple data modalities refer to:

  • Audio spectrogram analysis

In this method, Convolutional Neural Network models (CNN models), Recurrent Neural Networks (RNNs), Gated Recurrent Units (GRR) and Long Short-Term Memory networks (LSTMs) are used as the primary analysis tools. They are used for extracting features from a video or a static image and detecting artifacts typically “left” by a deepfake tool.

  • Video spatio-temporal features

This method employs a CNN to analyze audio data in order to differentiate between synthesized and genuine audios. The method is based on Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT). They are used for retrieving Fourier coefficients, converting them to decibels and then constructing a sound spectrogram. Deepfake audios are then detected using the intensity (“thickness”) of audio signal and its correlation with the frequency and time data. Successfully detecting deepfake audios can also serve as extra evidence in exposing a deepfake video.

  • Audio-video inconsistency analysis

This method matches video and audio analysis and can increase chances for successful deepfake detection. Inconsistency analysis is based on detecting dissimilarities between phonemes, which are sound units that distinguish words and visemes. Visemes are lip movements accompanying phonemes. By analyzing potential mismatches between them, this method can successfully detect a deepfake and discard it.


Algorithms Based on Heart Rate Estimation

Estimating the heart rate of the speaker in a video can lead to detection of facial manipulation. DeepFakesON-Phys is a detector that analyzes the heart rate of a speaker and uses the information to differentiate between a real speaker and a manipulated footage or a completely synthesized persona. This detector gathers data invisible to a naked eye such as oxygen concentration and illumination levels etc. Changing oxygen levels can have a direct impact on the appearance of a human such as changing face/skin colors. Additionally, temporal integration of frame-level scores are used to ensure more accurate results.

Face Morphing Attack Detection Methods


Morphing Attack Detection or MAD utilizes feature extraction method with the help of three descriptor types:

  • Texture descriptors. They will find changes left by the morphing process, such as artifacts in the eye region, etc.
  • Gradient-based descriptors. They take into consideration histogram calculations and properties of the feature vectors.
  • Descriptors learned by a deep neural network. They extract features from the footage for further analysis.

This method can use unaltered photos — passport or ID images — for reference.

References

  1. Video Rewrite, Origins of Deepfakes
  2. MelNet. A Generative Model for Audio in the Frequency Domain
  3. Top AI researchers race to detect ‘deepfake’ videos: ‘We are outgunned’
  4. Video featuring president Ali Bongo caused a turmoil in Gabon
  5. How to Produce a DeepFake Video in 5 Minutes
  6. 10k US Adult Faces Database
  7. Nasolabial folds
  8. Example of morphing detection
  9. Viseme detection in progress
  10. Expression swap is often used for animating historic paintings and sculptures
  11. Fake It Till You Make It. Face analysis in the wild using synthetic data alone
  12. Fake faces generated by thispersondoesnotexist.com
  13. Identity swap is popular among social media users
  14. Example of morphing two faces
  15. Attribute manipulation is simple to achieve
  16. Expression swap used to animate a painting
  17. Audio-to-video used for animating static images
  18. What is a phoneme?
  19. Visemes
  20. DeepFakes Detection Based on Heart Rate Estimation: Single- and Multi-frame